Looking for a plumber with expertise in fixing Bristan Shower to flow properly correct temperature

Hi. From your limited description... my guess is that you have a combi boiler supplying the hot water to the shower and likely you have already had it looked at. If so and it were my problem in my home then I would change for a 8.5 kw electric thermostatically controlled mains water shower and be done with it... allegedly. Cheers, Bob. Note: your feedback will be appreciated.

not sure what your trying to set? is it; electric? or mixer? how old is it? is pumped? hows is plumb in? ring the manufacturer up if your stuck, is more likley be carriage problem, if is a mixer,

The cartridge or valve has probably scaled up. Either take out and soak in vinegar and water for 24hrs or replace cartridge or valve.

Although the other plumbers comment is ok, and the job description is a little vague? I m guessing it’s a shower mixer valve. It could be that the flow is low due to blocked shower head ( the holes could be blocked up ) Or if when it’s running the water temperature is to cold , cool or intermittent , this could be the cartridge inside the shower body , which can be removed and replaced with new one. Or could be old combi boiler which could have a weak diverter valve diagram and when running hot water slowly ( as some shower heads are small)it’s not giving a signal for the boiler to run to give hot water.

I’d check the the hot at the taps was hot enough if so I’d try adjusting the thermostat or replacing it, but note the shower will only supply the hot water the the boiler provides