As one may notice with sterling, banknotes may look different depending on the bank they were issued from, with British sterling comprising of Northern Irish, Bank of England and Scottish banknotes, all worth the same, just printed differently.
There is a key difference though to be aware of when traveling to different destinations in the British Isles particularly with regards to Northern Ireland banknotes. Whilst Bank of England and Scotland banknotes are legal tender in Northern Ireland, Northern Irish banknotes aren’t fully accepted outside of the North, many shops and business in Britain don’t accept Northern Ireland issued sterling notes, so it’s best during your Ireland Vacation to either exchange or use them up upon leaving the North.