English pounds

Most likely not. Some businesses will accept, but not all. Easier using English pounds in NI, than vice versa. You can go into any bank and exchange them for English pounds without fee though. I think even the exchange places at the airport will honor them without fee (that I can't say from personal experience). You mention Ireland and pounds and I am assuming you are talking NI. If you have Euros from the Republic of Ireland, then that is another story.

I was in Northern Ireland last summer and had a couple hundred Northern Ireland pounds that I used in London later that year. I may have been lucky but buying food, tube tickets and theater tickets, didn't have a problem spending them.

Scottish and Northern Irish pounds should officially be legal in England, but some smaller businesses may be very reluctant to take them.

Thanks so much for your responses! I'm going to make a dash for London with the 45 pounds I have and get more money at an ATM in London, skipping the machines in Heathrow.

All transport from Heathrow, National Express coaches, London Underground and Heathrow Express/Connect trains you can buy tickets with a credit card at their ticket kiosks at Heathrow - you do not need cash.

I hope Bob or one of the other UK residents corrects me. But I read within the last year that the British issued new notes and that the old ones can only be exchanged at a very limited number of banks. (i have a stash of old ones to use up). Also years ago i ended up with Scottish notes from visiting there and changed them (very conveniently) at one of the banks when I returrned to London (i was told some stores were sceptical about accepting them)

Brian, that was the twenty pound note only - the previous design with a picture of Sir Edward Elgar on it is no longer valid.