Gareth Thomas is a confirmed guest for Nexus (work permitting).
I don't know if he's on the web site yet, but the address is www.enterthenexus.com
I recommend Nexus - I actually signed up for it this year *before* they announced Gareth as a guest. There's a couple of con diaries from the last Nexus on http://www.hermit.org/Blakes7 - I like it because they do an interesting alternative programme. It's only one strand, but it's well done and there were some very good speakers last time (my favourite session was one discussing the technical design of Thunderbird II, but then I'm a closet geek).
Judith