My Mrs has come to a similar conclusion from what she's read online and found a remedy which I'll try when I get home.
Sorry to hijack your thread @Archey but I've got a similar problem but it's too much pressure. It's a thermostatic shower fed from the combi boiler and it's as if the valve is letting too much cold through and it's cooling the incoming hot. It used to be ideal with the dial anti clockwise to around 11o'clock but it's just about ok on full (nearly round to 9 o'clock) but the pressure is too much. Can't see it being a boiler problem as hot water taps are very hot. Valve discontinued although they are still selling the same shower. Any thoughts? Probably going to be a new shower but I thought I'd ask...tia
Ar hey don’t know if anyone has asked but does the pressure drop on your tap in the kitchen or the bathroom if not it must be the shower itself.
Can you put a flow restrictor in the cold supply? Or, adjust the internal thermostat (I recently had to do that with my Mira Realm mixer).
As others have mentioned, it looks like an Aqualisa shower which is good news as spare parts are readily available from places like National Shower Spares or even from retailers on Amazon or EBay. The problem is almost definitely your thermostatic cartridge (virtually the only moving part on it) which can easily be changed and without hacking your tiles off the wall which is fortunate as it looks to be a built in shower valves. However you will have to first remove your faulty cartridge to see what colour the body of it is so you order the correct one (they are colour coded depending on water pressure. From memory pink, blue or black). Though while you have it out, if it looks limed up, just drop it in a glass of Coca Cola (seriously) overnight and that could dissolve the lime, lube it up with Vaseline (again, seriously) re-fit and it could work like a new ‘un. Obviously, isolate the water supply to the shower before removing the cartridge but I know you’re not that daft…. I don’t think
Shower update. Got home, ran it for 5/10 minutes, and it's working perfectly fine. Not sure whether it was just a frozen pipe, mains issue, poltergeist or what. Once again, thanks all.