Bloody boiler!

Does anyone know a good plumber in North Yorkshire? This thing has now packed up 4 times in two weeks. Each time someone from BG looks at it we get a different reason for the fault (basically it's overheating and cutting out). Had a new thermostat fitted at the weekend. Today it overheated again! No-one has said we need a new boiler, but maybe we do.
And it was my first day at work after a lovely week off. So, all in all not a good day.