Got help from divapor and lunns. They have identified it's this one GROHE-47450000 https://www.google.com/search?q=GROHE-47450000&rlz=1C1CHBF_en-GBGB878GB878&sourceid=chrome&ie=UTF-8
Replace the full tap component from the two wall connectors? Not sure that's DIY
And for the moment so I can reopen the mains, how do I put back the part I have unscrewed today please? I am trying but it doesn't engage and screw back in :(
My bathtub faucet is leaking. I have closed the mains and removed the only screw. This is on the cold/hot regulation handle. I see this now but I am not sure how I am supposed to extract the cartridge. Can you help please?