We are looking at these kinds of details at the moment and haven't reached a firm decision, but I think we're tending towards the former.

(For what it's worth, I prefer to look at it as the bid team's Wikimania bid, supported by Wikimedia UK, rather than as "a Wikimedia UK bid". But hairsplitting aside, I'm really glad that it's a bottom-up, volunteer-led bid which we are helping.)

Chris