THis may seem stupid, but at the game start what constitutes being in the start area, the whole base, the center dot, or any bit of the base at all?

Center dot.

Thanks Balduvian!

By the way, when you quote from errata and clarifications, where do you find 'em? I have tried to find them on the wizkids site and failed.

LOL, here read this thread and buried in there somewhere is the answer to your question about the E&R.

Yes, it is the dot. I had similar problems the first time I played a chariot, when it first came out. My opponent tried to get me disqualified because I started out with the entire front out of the area. The WL promptly told him the error of his ways:D.

My question is, does this work with single-based figues?

It should be center dot for any figure, but if you're in doubt about how your warlord will rule ask first.