I have just moved in and have a new shower and boiler. There is water pressure to the shower, but the water comes out cold. The boiler does not register when I turn on the hot water. It was working fine yesterday. There is hot water to the basin and bath.

Are you renting or did you buy this home? This sounds like a clogged hot inlet on the mixing valve

Just to clarify, there is water coming out when I switch to hot. It's just that its cold. When I checked what was happening on the boiler, the bier boiler didn't seem to recognise that I was demanding hot.

British gas had been out to adjust the boiler pressure the day before. Not sure if this is relevant.

What's the brand name of your shower valve? What I think has happened here is that when installing some minerals broke loose from the pipe walls and is now clogging the cartridge inlet ports, The solution would be to shut the water off, open up the valve and remove the cartridge. Check and clean the inlet ports. Now,(and this is important) Turn the water back on for a few seconds to flush out the supplies. Reassemble and test, Better now? Tom