I'd be curious to know this as I've considered checking out agents in the UK as well as here in the US.
I'll try to remember to ask at the conference, assuming I get my two 15-minute meetings with agents. One of them is offering a question-and-answer appointment rather than reading submissions, so he might be a good one to ask this sort of stuff.
I have to point out that there aren't many agents in the UK, and the ones who do SF&F are in a small minority. I shall of course submit to UK agents first, but I won't be surprised if I run out pretty quickly and have to try the US ones. It's either that or join the slush pile at Baen
(Not knocking Baen, BTW, but when they insist on a full and then state they take 9-12 months to reply, it doesn't exactly motivate me to put them at the top of my list!)