Due to one thing and another in Europe, in the Republic of Ireland where they use Euros, everything is rather expensive to people who use Euros and people who use Sterling.
What is becoming the case is that people close to the border of the Republic of Ireland and Northern Ireland, are coming into Northern Ireland to the border towns and spending Euros/converted Euros to Sterling in our shops and what not because it is cheaper. Doesn't exactly help their economy but its certainly boosting ours
Since all this credit crunch nonsence started...2 of our border stores in Newry (on the southern border) and Foyleside (on the north western border) sale have shot up over the past 2 years by about 128% if memory serves. Both stores taking in excess of £150'000 a week, with the majority being cross border trade. Just an example.
If it was unified currency, then if the US sneezed the whole world would feel it, and on those grounds I think thats why the UK has never adopted the Euro as of yet.
Interestingly enough...
Northern Ireland bank notes are not accepted in mainland England, yet its still pounds sterling and part of the UK. Scottish and English notes are accepted here.