Pipe inserts

[Carnegie]

I am replacing my old shower mixer valve, etc, and propose to replace it with an Aquilisa 'exposed valve' using their easy fix bracket which has 'push fit' pipe/supply connectors. The shower hot & cold feeds are supplied via flexible grey (marked 'Hepworth UK Barrier pipe') 15mm polybutylene (PB) pipes (in good condition).
In fixing the pipes to the new bracket connectors, do I need metal inserts or will standard PB inserts be okay? Also, whilst water is off, will standard 'push fit' stop ends be ok until I fit new bracket which will probably be a day or two later - I will fit the pipe inserts before placing in stop ends? I have an unvented high pressure system. Sorry if this is a bit basic for the expert plumbers!

 

[WHPES]

Can you get the old inserts out? If they are stuck in, dip the pipe ends in boiling water to loosen them. If not then you should be OK with Polypipe Polyplumb (black plastic) inserts but the new type of Hepworth inserts wont be compatable.

Push fit stop ends will keep the water in but make sure there are inserts in the pipe ends.

 

[Carnegie]

Can you get the old inserts out? If they are stuck in, dip the pipe ends in boiling water to loosen them. If not then you should be OK with Polypipe Polyplumb (black plastic) inserts but the new type of Hepworth inserts wont be compatable.

Push fit stop ends will keep the water in but make sure there are inserts in the pipe ends.

Thanks for that but can I just clarify your comment - currently, the pb pipes are fixed to the mixer valve with a compression joint which i will obviously undo when I remove old valve. I assume there must be inserts already in the pipe ends. That said, I will have to shorten the two supply pipes for re-positioned new valve and I presume I'll just have to fit the new inserts, as you recommend? - thanks for your help