My Brother just went sale agreed on his house in Donegal, buying a house in Derry. Only difference is he and his wife both work in the North and get paid in to a UK account, however the UK bank wouldn't even talk to them about a mortgage as their address was in the Republic. They found a mortgage broker who suggested they find a UK address just to use for correspondance whilst they got mortgage approved, they asked a Family member if they could use there address and proceeded to change address at bank, forwarded change of address to broker along with P60s etc and mortgage was approved withing a few weeks.