I think they usually do the voicing first, and the animation afterwards - hence how well they sync. I have no idea if they redub different versions from the same animation.

Yeah, the American one is better - the UK one is aimed at a Sunday afternoon audience and also for providing visuals for British Gas and the like; it's supposed to charm grandparents.

I don't think DerangedGoblin was praising the American version - at least I hope not. Both concepts are running the risk of being unfunny, but the American style is a cheesy, easy type of 'funny;' one step below, or maybe above physical humor.