I would be interested in going to a UK event, but don't discount liverpool as a venue we have the echo arena an a few other places to hold a large event in. Just don't let it get too commercial with it turning into a trade show there should be a place for trade but it shouldn't be the main event.
Also make it fun to attend have a few competitions like hack of the show, funyest gag of the show, spot the security services like they do at defcon.