Mixer shower valve not letting hot water through

[Procrastinator]

Hi. My daughter's mixer shower is not letting through any hot water. Lets through cold fine, but when it's turned towards hot the water gradually cuts off until nothing at all is coming through. No issues with bath or sinks in her fourth floor flat. Hot water cylinder (electric) is directly through the stud wall behind and slightly above the mixer. Both hot and cold are fed to the mixer via a Showermate Eco pump beside and slightly below the cylinder (same cupboard). That seems to be working but gets quite hot to the touch quite quickly when the shower is on. Not sure if that's normal.
Could the problem be a blockage in the hot outlet of the mixer valve? Thanks in anticipation (she's very stressed!)

 

[HERTS P&D]

Check the flexi's for any bloackages.
Turn the pump and water supply off to the pump first.

Andy

 

[Procrastinator]

Cheers Andy - I will indeed. Luckily there are stop valves in all the right places too, which makes a refreshing change