Replacement of worn sequential thermostatic shower valve cartridge using service pack SAR00.

How to replace the worn or faulty thermostatic shower valve cartridge with Ultra Group single sequential service pack (Ultra, Hudson Reed, Premier) SAR00. Instructions include temperature adjustment.
For temperature adjustment, set the shower to the hottest setting (turning the handle fully anti-clockwise so full on) then insert a 2mm Allen key into the hole which holds the handle screw as shown in the video. To increase the temperature, turn the grub screw with the key anticlockwise or clockwise to decrease the temperature by a quarter of a turn. The instructions are the same procedure for either concealed or exposed valve.
The shower has one handle it will be off and as you turn the valve handle anticlockwise it will run from cold to hot, so there is no separate flow control.
The issues were sticking control, no end stop and water temperature getting too hot.
This shower valve uses a wax thermostatic cartridge to maintain a constant shower temperature.
Warning: You must shut off the mains water supply before starting..
For guidance only as I am not a plumber.