Best way to cover chased pipes

Hi all, I am about to chase some rad pipes into my wall, but not sure of the best way to cover them before the plaster comes and skims...

Firstly I know about the regs for the depth of the chase and I understand I need to cover the pipes and allow for expansion.

My plasterer is a friend and not an expert so doesn't like doing the binding layers and filling in large holes, so ideally I need to find a solution which will allow him just to skim over everything.

What I was thinking of doing was simply putting plasterboard over the channel I chased and attaching it with the expanding foam glue stuff. Only problem is I haven't seen anyone suggest that on the internet so I'm thinking it's a stupid suggestion!!

Any advise would be much appreciated

I insert plastic conduit over the pipe, I assume they are going to be copper, but if you are using plasterboard just use amalgamating tape as a protection against corrosion where in contact with limestone walls and leave some expansion space.