The English.
In discussions like this, the meaing of words is critically important. Your use of the term "Brtish" is still ambiguous. http://en.wikipedia.org/wiki/British_Isles_%28terminology%29 should give you some insight.
British notionally means someone with a UK passport, which includes the non-foreign residents of Northern Ireland. Surely that is not your intent. Is it possible to parse the Irish from non-Irish in Northern Ireland today. Its like trying to parse New Yorkers from New Jerseyians (sp?). How long does you family have to be there before you get a voice?
There aren't many English in Ireland so if they left it wouldn't make a blind bit of difference.
Anyway, the troubles ended on 9/11. The IRA knew they couldn't kill toddlers in Shopping Malls and still expect American sympathy.
Northern Ireland is part of the UK until the people of Northern Ireland decide otherwise. That is accepted by the Republic of Ireland, Britain, the DUP, UUP, SDLP and Sinn Fein.