The bank of England belongs, in part, to Scotland. The fact that it is currently administered from Westminster doesn't make it an English asset. Your characterisation of Scotland as being a 'petulant teenager', provided for, in this case in terms of borrowing power, by the UK allowing us to use their bank is erroneous.
Personally, I'm fine with Scotland foregoing a share of it, though. I would prefer to see us use our own currency, however. We'd start debt free and, being a net exporter, would in a very short time have a surplus of foreign currency with which to underpin our own national reserve bank.