you need identfication with your photo on it to go to anywhere. driving licence.
, may do, but if you have a passport then that would probably be the wisest thing to cover all bases.
Further to the above answers, the Common Travel Area allows for citizens of the Republic of Ireland, the United Kingdom and the Crown Dependencies, i.e. the Isle of Man and the Bailiwicks of Jersey and Guernsey (which includes Alderney, Sark, Herm and other islets), to travel between their countries without a passport.