I have one and I've switched some bits and pieces out of the other offsetting accounts I have but will be keeping at least one open until they let us know what is to happen with the offset mortgages as obviously the whole point of them is that there is a current/deposit account linked to it to offset against it. I can get to the stage where the current account linked is used for nothing other than the offsetting but will leave an offsetting deposit open too as why pay fees on the current one when the deposit will do! But have to wait and see what solution they are going to come up with. I have seen a poster, can't remember where, who obviously works for UB saying it's a possibility they will keep them in some way and operate remotely as they have no other solution.
As they have made no deal to transfer their trackers anywhere I don't think they know themselves what they will do with them!