Baxi 105e combi boiler - fan problem?

I have a 9 year old Baxi 105e combi, which has been regularly seviced and has had a hot water diaphragm replaced 2 years ago. Just recently the boiler has been failing after about 20 to 30 minutes, with the flashing red 'fan' symbol showing. No heating but the pump is still running, and no hot water. It works again after the next timed cycle, but again stops after a short period. My local gas fitter has replaced the PCB (twice) and has tested the fan but is now stuck. Any advice would be much appreciated.