Its a combi bolier and is serviced but Engineers have not found reason
u can isolate the radiators from the boiler using the isolation valves fitted on the bottom of the boiler. if the pressure stays the same u are losing pressure in the radiators,if the pressure still drops u r losing pressure in the boiler.before u isolate the radiators make sure the boiler is set for hot water only.u could also change your engineer
If this is Forced hot water then to lose pressure is to lose water. You need to find the leak which should be easy. if you have no leak then the pressure reducing valve may need to be replaced, but once again there must be a leak to allow the pressure to be released. the pressure is releasing somewhere. Where is teh question.
