If the boiler is still faulty why is it not 1 continuous job? Any advice gratefully received

Hello, your local council's citizens advice bureau/trading standards department helpline will advise you in great detail of your rights. If you have asked for a specific repair and the company have not fixed the issue that they were called out to do and are now being difficult, trading standards will tell you exactly how to deal with them and what articles and sections to quote from which act(s) in law. If, however there was more than one fault on the boiler and they have fixed one of them then it might be a bit more complicated. When I carry out work which may have more than one fault, I am very clear from the beginning if I suspect there is more than one fault, for example a faulty electro-mechanical fan is nothing whatsoever to do with a sludged/scaled/kettling water heat exchanger but both could make a noise on the same boiler. Fans would tend to make spinning/grinding/rumbling, scraping and buzzing noises rather than banging. Banging noises are more likely to be kettling, overheating due to faulty thermostat or poor circulation, gas ignition issues, water related pressure issues. Maybe on your boiler, the fan was heard to be grinding a bit and 'on its way out' but the banging noise was the heat exchanger. They may have replaced a fan which might not have lasted the winter but that wasn't actually what you called them out to do. You may need to actually ask them why the fan was replaced for a banging noise and how they diagnosed this. It sounds like a wrong guess to me but I can't really say as I've not been onsite. Hope this helps.

Every company is different, some are, 1 part 1 job, some are until issue is resolved, myself and most local one man bands I know of would make sure everyone is satisfied before asking for payment. It sounds like you had multiple faults if one part has changed and now it sounds different, this should have been talked about with both parties at the time.