My mother recently had a Worcester Bosch Greenstar 18Ri installed. Heating hot water is fine. To start with 4/10 radiators were working. Called installer who bleed radiators, installed a new pump in boiler and then fitted some sort of red external pump with a filling loop, charging her £575 for 3 visits and parts. Now 8/10 radiators are working and she is having to call him back. The radiators have TRVs fitted and the system was power flushed. Does it make sense what he's done so far? or could it be a case of boiler not being sufficient for 10 radiators. There could be a genuine problem with the system, but I'm getting worried how much more it's going to cost her to put it right, as her only income is her pension.