If all the heating is UFH simply run the boiler at the required temperature - no TMV, pump or anything required. If you have a mix of ufh and rads then you need to run at higher temps for the rads so you need the mixing valve etc and lose the slight extra efficiency you get running a condensing boiler at lower temperatures. But you're probably losing a lot more by heating with rads rather than ufh anyway.
Please forgive my ignorance but you imply it is possible to set the flow temperature of a combi to suit the ufh coils? Does this mean that the flow to UFH halts while there is a demand for hot (50C) water from a tap?
In my case I have installed only a towel rail in the shower room in addition to the ufh coils.
AJH
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