I've just had a plumber connect up a couple of new radiators today (yeah, I
know; but I run out of time) using 10mm microbore.

After some discussion, as it's an essentially solid floor, he's ended up
running the microbore concealed behind the skirting, and the flow and
return emerge from the wall just above the skirting from what is now a 1"
square hole in the plaster (the wall structure is solid brick with internal
sand-cement plaster).

My question is, what would be the best way of filling these holes back to a
flush surface, so that the surface doesn't crack when the pipes get hot?
The wall is currently freshly skimmed and will be emulsioned when the
plumbing etc is done.

Thanks

--
David