I was having a banknote argument only yesterday. I knew I'd heard somewhere that bank of England banknotes were only legal tender in England and Wales, and other forms of paper money were representative of money (rather than actually *being* money). In fact, I probably heard this on Mudcat....
Bank of England website says:
The concept of legal tender is often misunderstood. Contrary to popular opinion, legal tender is not a means of payment that must be accepted by the parties to a transaction, but rather a legally defined means of payment that should not be refused by a creditor in satisfaction of a debt.

The current series of Bank of England notes are legal tender in England and Wales, although not in Scotland or Northern Ireland, where the only currency carrying legal tender status for unlimited amounts is the one pound and two pound coins.

So we're all just using make-believe mickey mouse money after all.
I agree about the Euro though.Oh, but a lot of places in Norn Iron take Euros now, certainly in Belfast.