thermostatic shower playing up

Carrot007

Well after a year or so of being hard to turn colder and me ignoring it as long as the temperature achieved was ok, the shower suddenly decided molten lava was the appropriate temperature!

I took of the "turny bit" (advanced tecnical term there!) and have got it turning easier but there is about a 0.5 degree turn now beetween cold and boiling. I guess it need changing!

So how easy is this? How do I know the right part to get? Do I need to turn the water off or is having the other end of the mixer off enough! As those sorts of questions.

I have no idea the model it is. It sort of looks like this one https://www.plumbworld.co.uk/architeckt-round-thermostatic-mixer-shower-with-round-drench-head-872-32466 if the output secector and shower hose bit was the other way round! The water control is on the left and the temperatre that is being a pain is on the right.

Hopefully the can guide me as I am sure I am capable of this (I have fitted a basic bathroom before, just never dealt with a shower like this!). I'm sure knowing the price of the parts I would resent having to get a plumber in!