Set Square wrote:

I hope not! This unit is designed for stored water systems only - and needs
to get its cold feed from the header tank, *not* from the mains. I presume
that it *is* correctly plumbed?

It does its feed from the cold tank.

If hot water isn't getting through properly, there could possibly be a
partial blockage in the pipe. If this is the case, you may be able to clear
it by disconnecting the hot supply at the unit, and back-flushing it with
mains water.

Difficult (for me at least) as the pipes are in the wall and go into the shower
unit from the back.

Alternatively, there may be some adjustments inside the unit which limit how
far the mixing valve can move in the hot direction. [It needs to move more
in winter than in summer anyway, because the cold supply is colder]. Have
you got an installation manual?

Yes I have an installation manual. It gives instructions as to how to
disassemble it, but they're quite daunting to someone of my limited skills and
experience!

Glenn.