I have recently installed a set of second-hand mixer bath taps.

Facing the taps, to the left is a circular on/off control, to the right
is a circular hot/cold control and in the middle is a pull-up plunger to
divert to the shower head.

My problem is that whilst I know my hot water is very hot, this tap is
always mixing some cold in, even when on fully hot, so my wife is
complaining her baths are cold.

I've not inspected the tap closely yet, but it looks as if the hot/cold
end will fully unscrew. Is there likely to be any adjustment to reduce
the amount of cold mixing in, could it be designed like that for safety
(I know that in some installations they have to limit the maximum
temperature) or is it just FUBAR'd?

Cheers

Peter