Yes, RCP, UFO was (and is!) one of my fave Gerry Anderson series. It was a bit more adult than thunderbirds, with Cmdr Straker having marital problems, etc. Also, the way the "aliens" were shown is good and clever, we're given just enough hints about what they're doing to cause unease, but never shown anything directly (it's usually a mistake to "show the monster", unless it's a really good one, eg daleks!).
In comparison, I find Space 1999 rather diappointing! A very misguided attempt to "compete" with Star Trek (which wasn't about "special effects", but the "characters", something Space 1999 didn't have!).
(Having said that, how about Gabrielle Drake? Corr .... especially if you like purple hair!
http://en.wikipedia.org/wiki/Gabrielle_Drake ).
(interestingly, v famoous actor/playwright Steve Berkoff also had a minor UFO role, as an interceptor pilot:
http://www.iainfisher.com/berkoff.html Also - "more officially" -
www.stevenberkoff.com).