Re: Registered office.
Where the RBS jobs will be located will depend upon where the company is headquartered, and whom owns most of the shares. If the UK continues to own most of the shares after independence, and this seems likely, then it would be politically impossible for UK taxes to pay Scotish wages - the jobs would have to be repatriated.
The only way they would remain in place is if the Salmond (Scots currency) depreciates against Sterling to the point of being competetive with India, though that would hardly be a victory for the Plaid Piper.