Still no evidence of your qualifications then?
Quality combis rarely pack up. You get what you pay for. Try an Intergas. Backup? Kettles and Qooker taps are popular. Appliances are all cold fill these days. Backup shower? Try an in-line electric shower heater. The boiler down on your combi or unvented cylinder? Throw the switch. Never thought of that did you?I don't think you have any idea how often combis pack up and the hot waters lost, and it's often at the most inconvenient times.
Good luck finding anyone to fix anything.Good luck finding anyone to fix your combi at the moment...most of us in the gas trade are 50+ and few of us are risking working at the moment.
How about a graduate engineer. We do not like being told what to do by guys who swing on stilsons.Still no evidence of your qualifications then?