As there are quite a few SFO's upgrading to Captain at EDI/GLA the waiting times to get into the bases will not be long. Last time I checked (a couple of months ago) there were no FO's waiting to get into these bases.
The difficulty will come when it is time to upgrade to the LHS as spaces are few and far between at these bases. It is already becoming dead mans shoes with about 9 people on the EDI waiting list looking for a Captains position at the base. With a three aircraft base you could be looking at a 2 year wait if you're number 9.