Estimated boiler repair costs in N7 range from the cheapest Boiler repair £120 (Heat Input Plumbers based in NW5) to the dearest Boiler repair £220 (FixGas based in N4). This is an average cost, replacing a heat exchanger will be more expensive, a diverter valve less so.
Comparing gas heating engineer estimates for boiler repairs in N7 gives you an idea of who will be better value but the best way to compare costs is to get actual quotes.
What to do - If your boiler is playing up, quickly get rates and quotes for boiler repairs by clicking "Get quotes" to post your job to heating engineers in N7

"Boiler repair : replace AAV on a Vaillant ecoTEC pro boiler. The boiler was recently serviced, so only this repair is needed. "
N5
"I need my Boiler service"
N4