My procedure is the same as Tony does. I charge to diagnose the fault and if the part is cheaper supplied on a fixed price repair than thats what I advise to the customer.
Recently I was asked to replace a Suprima PCB which costs about £170 so I suggested a BG repair at about £190 would be cheaper for him.
The customer said that he had such bad experiences with BG in the past that he preferred to pay me £254 rather than having them in the house!
Tony
Exactly, I also charge a diagnostic charge which includes an assessment of the cost of the repair/s and then the customer has the option as Tony say's above.
The most I've ever charged for a boiler repair has been about £500 but that included two parts and a boiler breakdown in one of the coldest winters in the last 30 years up here in Glasgow with plumbers in real short supply however the parts cost about £350 and there was no chance of getting a boiler manufacturer's service engineer or indeed even BG out for any sort of repair so the customer wanted me to do the work.
BTW, most of my jobs only take an hour at the most and if the job is going to run into the three, four, five hour mark then I tell the customer this and give them a cost for the work before I do anything else.
In my experience most boiler faults will take no more than two hours labour with the exception of the hell that is the WB 24 CDi divertor valve replacement but these I pass on to WB as a matter of course anyway, so why then did this guy have to charge for five hours or more labour?