Jamie came to look at our cylinder after it started making some loud banging noises. He helpfully explained the makeup of the boiler (something that previous plumbers hadn't bothered to do) and what was wrong, and then came back a few days later with a couple of colleagues to replace the pressure relief valve, reinflate the internal air gap, and replace some of the piping, plus adding an on-off switch for the mains water so we could reinflate the air gap ourselves in the future without having to call out a plumber. He also came another time to check our boiler for possible gas issues. He arrived very quickly, performed the tests, put the boiler back together and fixed the broken reset button in the process, charging us a very reasonable rate for the work. Jamie is very helpful, professional, and quick to respond when we have problems (our boiler and cylinder are both very old and have had repeated issues recently).