I remember first seeing it in 1993, when in the summer the series was first re-aired on Dutch television, and weeks later the entire series was aired on BBC1 (on Fridays at 6 PM). Soon I had the entire set of Matchbox vehicles and figurines (twice, eventually!), and I also tried to build my own Tracy Island after the famous Blue Peter episode that showed you how to do it (as Matchbox simply couldn't produce enough due to popular demand!)
Later, of course, came the repeats of Stingray (which predated Thunderbirds) and Captain Scarlet (one of Gerry Anderson's later series), which hooked me even further.
Even so, Thunderbirds remained the more favourite of his series - such was its popular impact, that famously, the Concorde prototype was rolled out to the tunes of the
Thunderbirds March a couple of years later.
Here's the first episode of Thunderbirds (1965) on Youtube:
http://www.youtube.com/watch?v=4U6eY3ZA5XQ
... the first episode of Stingray (1964):
http://www.youtube.com/watch?v=6Lp-PIfZMSs
An finally, for a very interesting comparison: here's the first episode of
Captain Scarlet and the Mysterons (1967):
http://www.youtube.com/watch?v=nx412jDfjNc
... and what happened when Gerry Anderson discovered CG (New Captain Scarlet, 2005):
http://www.youtube.com/watch?v=X3JBnRh8OCc
Also, his work inspired many in the FS community: so, for instance, Libardo Guzman who not too long ago released a magnificent model of Thunderbird 2:
(Incidently, I think they're looking for my lost airmen as well - that means it won't take long for them to be found now...)
Nikko