Funny,just this past Feburury I purchased Scottish notes from an ATM in North Berwick. Note, Bank of Scotland notes. I spend 30 pounds paying for my B&B in St. Bees, ENGLAND and at the Queens pub in ENGLAND. The rest were spent at a pub in the Paddington area in London ENGLAND. Boy, guess I sure fooled them!!!

David is spot on. stfc is not

As we're planning a trip to Northern Ireland and I've been doing my homework, I was curious about pounds from there (we've not been) as well as from Scotland (we've been multiple times). Hence, I went first to Wikipedia where I got an interesting (and likely valid) description of legal tender.

Next, I came here and did a search and was reminded of our leaving Scotland once with a tanner from there inadvertently. When I asked a petrol station owner a few miles into England about it, she said she'd take any kind of money.

The points made above about banks in England accepting other pounds are borne out by the Wikipedia article.