When Scotland goes Independent we wouldn't want our frontline assets in a foreign country?
We've had our frontline assets in foreign countries before when facing a threat. RAF Germany worked fine, if Scotland (and Wales) went independent then RAF Scotland (RAF Wales) would work just as well.
These aren't England's assets I'm afraid chaps, but the UK's. If the UK were to dissolve then these UK assets would likely have to be divvied-up between the (former) constituent members, as was the case for the Soviet Union/Yugoslavia etc.
In these cases this was mostly done on a 'whatever's on your territory is yours' kind-of-a-fashion. On that basis, the P-8s would be Scotland's.