Currency!

[Kirobaito]

If Granny ever gives you any Northern Irish money you'll need to get that changed at the bank because most places seem to think it's not legit

While I was in Canterbury I handed a lady a 20-pound purple Walter Scott HBoS note (now that Lloyds bought them, is HBoS money still circulating?). She had to ask someone else, who presumably was a Scot, if it was actually legit money or if I was trying to pull a fast one on her.

EDIT: The Republic of Ireland uses the Euro. Northern Ireland uses the pound, but their own banks print them out. There's no such thing as merely a "20-pound note." There are several banks which print money, so their notes do not all look the same. In England the BoE has a monopoly, but in Scotland there are either two or three, and in Northern Ireland there are four.

EDIT 2: And of course, you need to edit your "rest of Great Britain" line once you get over to the UK - of course, Ireland is not a part of Great Britain, which is merely an island that includes Scotland, Wales, and England.