The message
from ChrisJ contains
these words:

Also is it a big job to run the wet UFH at different times to the rest
of the house central heating?

Depends on which system you've opted for. If it's part of the main
radiator circuit, then it's not really possible unless you're going to
run round turning off all the valves. If it's got its own pump or is
plumbed back to the CH/HW valve then it's trivial.

--
Skipweasel
Pay no attention to that man behind the curtain.