Plastic H & C piping

I want to re-run a lot of my unsightly visible plumbing in the now internal cavity wall between my extension and old property. I thought that if I take out the odd bricks I can use PEX piping for H & C and heating, by feeding it between floors because it is reasonably flexible. I thought I would be able to support it by occasionaly injecting canister foam after taking out bricks; into the cavity round the pipes. Is this all feasible??
Is Pex barrier pipe ok to use in such circumstances?
Is there any reaction between the foam and barrier pipe that will cause problems.
Which type of barrier pipe is best to be able to use standard brass compression fittings with, as I don't like push ons too much. B&Q sell two makes and I would be using both 15 and 22 mm equivalents.
I've had a lot of experience of copper plumbing but none with plastic.
Any help please????
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