Travelling around UK and Ireland by for 80 days in 2014. Crossing from Holyhead to Dublin and finish in Belfast and then across to CairnRyan or Stranraer. Do rental companies allow the car to be taken across to Ireland and if so I presume that there is an extra cost for doing so. Or do you dump the car at Holyhead - hire another in Ireland and dump it in Belfast and hire again at Cairnryan. I'd prefer to use the same car all the way without the hassle and cost of changing cars.