Update. Finally took the plunge yesterday morning and cut the hot water
pipe, and fitted the compression stop end. This morning, still no drips
or weeping :-) Tempted, of course, to nip it up a fraction 'just in
case', but will leave well alone.

The pipe slicer is a wizard tool.

Basin, shower and WC all out, the only remaining job being properly
blocking the wastes to prevent smells wafting in. Currently sealed with
plastic bags and rubber bands.

Thanks, all.
--
Graeme