how to replace a multiblock valve on a unvented cylinder

alot of plumbers have different names for a multi block valve / PRV like combination valve or cluster valve or even inlet valve.
these commonly breakdown and drip from the discharge pipe after a service.
its a simple job and having the understanding of the safety features when learning for bpec or any unvented training, this will help.
so how to install one...

[@AlexRocks24-7]

Mate, you should have changed that flexible pipe 🤦

[@professorplumb]

Changed? I will on a service

[@AlexRocks24-7]

@@professorplumb you know that flexible pipe is illegal 🫤 I would have done it there and then.

[@professorplumb]

@@AlexRocks24-7 fair enough, i’ll have to sort it on a service but im up against it today