Thermostatic shower/combi boiler temperature problem?

Hello - I have a 3/4" dual control thermostatic shower, run by a combi boiler, and the shower rarely gets hot enough. Have tried the following - all the usual temperature control stuff in the manual, and it didn't work. Have now taken the valve apart and removed the thermostatic cartridge completely,... show more Hello - I have a 3/4" dual control thermostatic shower, run by a combi boiler, and the shower rarely gets hot enough. Have tried the following - all the usual temperature control stuff in the manual, and it didn't work. Have now taken the valve apart and removed the thermostatic cartridge completely, making it slightly better.
I need to somehow trick the shower into thinking it's never hot enough, so it shuts off the cold water going into the valve, and then i can just control the temperature using the water pressure going through the combi. Thought i could do that by removing the cartridge which has helped, but not enough. I have worked out the problem is definitely not to do with the boiler, as the hot water inlet on the shower valve is red hot, while the water is lukewarm.
The actual make of shower is not mentioned on the manual - it's a victorian style one from MFI.

Any ideas?
Pete
4 answers 4