Shower valve problem

[Compostella]

I posted last week about my shower valve.

Thought I'd sussed it, and I have in a way but its not quite right:

On the advice of a plumber, I removed the non-return valves from each inlet of the shower valve. Now when I turn the shower on, the water comes out fine and the pump kicks in.

Great..................but the temperature control is the same knob as the one that turns it on i.e. you turn the knob and it come on and the more you carry on turning the hotter it gets. The coldest I can get it is about the right temp for a shower.

How should i rectify this, should I put one of the non-return valves back in?

[markja]

would putting an inline valve/tap (or putting the non r.v. ) on the hot water feed and restricting the flow help? then the cold would be at an advantage. ( make sure the cold is not being restricted first. )