I've recently been deliberating over which group to join, too.
Being based in the more Northerly part of Warwickshire, it does seem best to go with MROC for now -- I've approached them via their site -- but thought I'd drop a message in this old thread in case anyone had further thoughts on the matter.
Presumably the
map still shows Warwickshire "greyed out" because MROCResponse came on board relatively recently I think?
Cheers,
James.