I'm in the same boat as you. Have my sterling deposits with UB in the North. My own view is that the RBS, parent of UB are 83% owned by HM Government. As the UK have and control their own currency, my own belief is that they are working through the problems and should hopefully come out of the disaster area in a few years.
Other than that I would have less faith in Santander which are Spanish, (look at their circumstance) and Halifax which are part owned by the UK Govt, but to a much lessor extent.