Im a dual Irish?
Very little, given that under the Ireland Act, 1949, Irish citizens resident in the United Kingdom enjoy almost identical rights to British citizens, although it remains to be seen what immigration queue youll go through at airports, as there are proposals to have lanes for British passport holders. As regards your British citizenship, the fact that you choose not to renew it does not mean that you cease to be a British citizen, unless you actively choose to renounce it, which costs money - you might as well go to Ireland and hand your passport in at the British Embassy in Dublin.