Mistral:
Well now, there's an interesting ingame/outgame debate. I mean, _are_they really British (descended) characters just because of the actors'accents? Is Blake Welsh, Jarriere Scottish? If so, then we may really have to account for the differences between the Travii.
As Blake and Avon both worked on the matter transmission project, they must both have inhabited the same Dome at one point (I assume Domes are large enough that people would live and work in the same one). Although there's no evidence that this is the same Dome as the one we later see Blake living in, it might be a reasonable assumption that they are close? Certainly the landscape we see in TWB looks British, though it's hard to tell in the dark.
There's no reason to suppose the other Earth natives came from the same region at all, though the fact that they all speak with similar accents suggests that they might.
The only place I can recall anyone mentioning on Earth offhand is the Himalayas (Vila). I don't think that they were his homeland...
Tavia http://www.viragene.com/