On 02/10/2020 11:42, Theo wrote:
snip
(although I don't know how the boiler copes with a mixed UFH/radiator system
- I assume the UFH isn't going to run at radiator temperatures? Is there a
thermostatic mixer?)

There is a thermal mixer on the UFH manifolds but having marginally
up-sized radiators in the bedrooms (downstairs/under ground) it's
enabled me to run upstairs living area (6 UFH zones)and downstairs
radiators all at a max. temp of 55 degrees when it's 9 degrees outside
with a reducing boiler temp as outside temp rises.

Might be a different story in "normal" house though.