In reply to Oujmik:
Looks like the third one to me?
https://www.plumbworld.co.uk/round-concealed-shower-valves-1060-0000
Given the tiling you may be better taking it to pieces, I can't see how you'd replace it without having to re-tile.
It may he possible to get a cartridge if you can identify it.
Or take it to bits and soak it all in vinegar.
Grohe do some similar shaped valves and they are good quality.
Your plumber went for the cheap and easy option in my opinion.
Post edited at 22:01