Welcome to the thread, Andrew!
Great to have another fan of the show here!!
I will try and answer your questions- I know the answers to some of them, others I am just guessing based on the information I have. So if I answer incorrectly and if anyone else knows more and can correct me, then please do!!
Was this always conceived as a two-series thing, or was it due to the success of Girl From Tomorrow that the second series was made?
Mark Shirrefs and John Thomson had envisioned the complete story before both series were scripted and produced - during the first series, there were some brief references made to The Great Disaster, for example when PJ projects a hologram in Jenny and Petey’s cubby house that shows the Earth in the year 3000, you can see the damage to the Northern Hemisphere, and Silverthorn gives a description of what life was like in his time and how “clean water is more precious than gold”. But these themes weren’t fully explored until the second series as it wasn’t possible to tell the whole story within 12 episodes.
Also, it was pretty clear that there was more of the story to come, with the first series ending on such a huge cliffhanger with Jenny being paralysed and the stressful and rushed departure of Alana and Jenny as Jenny’s worried family looked on. So definitely 2 series were planned, but at the time the first series came out I’m guessing that the writers didn’t know for sure that a sequel would be made- that depended on how well the first series was received. And when it was a success, production for Tomorrow’s End got under way.
Were the two series made back to back or a year/years apart?
I don’t know whether the first series was filmed in 1989 or in 1990, but I know that it was first shown in Australia in 1990.
The script for the second series was typed by Mark Shirrefs between January 2nd and January 5th 1991- he worked from home and could stay up until 2am finishing the episodes. Then the filming of Tomorrow’s End was in early 1991. So there wasn’t a very long gap between the 2 series, but I couldn’t help noticing that James Findlay who played Petey had grown a little bit between TGFT and Tomorrow’s End (little kids grow very quickly!!
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Did the show have a good budget or not?
It didn’t have a Hollywood budget, but they did get a decent budget to make the show from the government agency, Film Finance Corporation Australia, which had a rule that a certain number of hours of Australian television each year would be filled with children’s TV funded by the Australian Government. These high quality shows would also be sold to broadcasters overseas (like the BBC) and that way the agency would recoup the funding through the overseas success of the shows. Round The Twist and Spellbinder were also funded by the Film Finance Corporation.
I’m guessing that the budget for Tomorrow’s End was bigger than for the first series as more sets needed to be built for the scenes set in 2500, whereas most of The Girl From Tomorrow was filmed in existing locations for the scenes in 1990. Also a lot of the money would have gone on adding special effects (which were basic by today’s standards but were advanced at the time!)
Was it a happy shoot or a difficult one?
There is very little behind the scenes information out there as I haven’t seen any interviews with cast members about what it was like shooting the show, other than in the 10 minute documentary Making The Girl From Tomorrow. From what I saw on the documentary, James Findlay really enjoyed being in it, and Katharine Cullen and Melissa Marshall got along well, making a promise to keep in touch after the show was over. It would be wonderful to see a reunion interview with former cast members reminiscing about their memories of being in The Girl From Tomorrow! But it was a long time ago and the actors went on to do other things…
The only cast member I have personally been in touch with to talk about the show was John Howard, who had positive memories of making it- from the sounds of it, there was an enjoyable atmosphere on set for most people involved, going by what I saw in the documentary and what John told me.
John really enjoyed shooting the beach scene in Tomorrow’s End when Silverthorn dived into the sea to rescue the drowning boy. John said that originally it had been planned that a stunt actor would stand in for him, because the sea was quite dangerous in that area, but John, who passionately loves the ocean and is a very strong swimmer, insisted on doing it himself.
John also told me that he got along well with Miles Buchanan who played Eddie. I asked John if it took a few takes to shoot some of the more physical scenes they did together (like when the TV exploded and when Silverthorn would grab Eddie and rough him up) and he said that they managed to do most of those scenes in one take. John was impressed with the very high standard of Miles’ acting and said that Miles was a lovely person- he spoke affectionately about him.
Behind the scenes, Miles was battling with severe depression and addictions, but nevertheless did a stellar job (watching the show as a kid, I would never have imagined what Miles was going through).
A bit of behind the scenes trivia: the technician who operated the Moddie Chamber was played by Elizabeth Maywald, who was married to John H at the time of filming- they had a son together later that year.
Was there ever a plan for a third series or a spin-off?
No, as all the threads of the story were wrapped up at the end of Tomorrow’s End and it had been decided by the team of scientists that there would be no further time travel because of the dangerous changes to history it caused…but I would absolutely have loved to have seen a spin off show with Silverthorn and Eddie, or with Silverthorn and his gang in 2500!!
Ties into first question, but when writing the first series, did they have an ending in mind for the second series?
As I said, they had already written the full story, but during the course of making the show many parts of the story and the dialogue were adjusted. There are many differences between the books and the show episodes, and between some of the original scripts and the finished episodes, so the writers and script editors did change their minds about some of the scenes and minor details of the story, but I’m assuming the basic details of the ending would have been planned out from the beginning when the show was being pitched to be made.
Why no Tulista in Tomorrow's End?
Great question!! I always thought her absence was odd too, especially considering the close emotional bond we saw between Alana and Tulista during the very first episode. The book version of Tomorrow’s End (which I didn’t get to read until 2018) provides an answer…
But even so, personally I have always suspected that originally it had been intended that Tulista would accompany Alana on her time journey to 2500 in Tomorrow’s End (which would have made sense as Tulista had spent a month in 2500, had experience and had learned the dangers, but no one else from the year 3000 had been there before), but for whatever reason, the actress Helen Jones who had played Tulista was unavailable to return for the second series. My theory is that rather than recast the part of Tulista, the writers created a new character, Lorien, to be Alana’s travel companion.
The sudden appearance of Lorien in the second series always felt odd to me… she was supposed to be Bruno’s assistant on the Time Travel project, but she wasn’t even in the Time Lab when the first time journey took place!!
Plus the book’s explanation about Tulista going to the Northern Hemisphere so soon after the events of the first series (ESPECIALLY as in the book version, when Jenny woke up in the year 3000, Alana told her she’d been there for only 9 days since the events of the first series, not a month as in the show) also seems odd considering the traumatic ordeals Tulista and Alana had just been through.
Tulista was like a mother to Alana, and had been separated from Alana for a month during her stay in 2500. Alana had also been separated from Tulista for a month when she was stranded in 1990, missing her and replaying her holographic recording, and not knowing if she would ever be able to return home and see her guardian in the flesh EVER AGAIN!! And I know that people from the year 3000 were trained to be less emotional, but if I had been in Alana or Tulista’s position, I’m sure I’d want to spend lots of time together after my ordeal, and share experiences of our time journeys. For Tulista to fly out to the Northern Hemisphere and leave Alana again, so soon… it just seemed weird to me.
Note, this is NOT intended as a criticism of the writers or of the character Lorien, or Catherine McClements who played her!! It’s just a theory I have, and I think that if Helen Jones wasn’t available then it was a smart solution to create Lorien because for younger viewers, a recast of Tulista- seeing a character with her name but with a different face- would have been confusing.
Speaking of Tulista, it was funny that when she got dressed up in armour for her time journey, she told Arva that “This was what women wore in 2500”, but when the characters travelled to 2500 in the second series, the only other woman there wearing armour was Silverthorn’s sidekick Kroll!! And no ordinary civilian men wore armour either. So I interpret this as the historians of 3000 making an unfortunate mistake basing Tulista’s clothing on historical images they had of female armed gang members from 2500. Which probably was the reason why Tulista caught Silverthorn’s attention… I imagine that initially he mistook her for a member of a rival gang!!
Great to have another fan of the show here!! 
However, we used TGFT books as a reference. They helped a lot with many lines pronounced in a... uhm... quintessentially Australian way. 
