UFH from the end of the radiator loop

[Stinsy]

I was wondering whether to put UFH in a room outside the footprint of the rest of the house (where it would be much prefereable to the radiator already there) but I realised that UFH prefers continuous low-temp input (often done out-of-hours,) whereas we run the gas central heating when we are up and about or likely to be sedentary, plus warming-up time beforehand. I had the impression that the intermittent relatively high temperature water circuit wouldn't work very well with a slab heat store.

The old-fashioned central heating provides background heat by most people's standards, plus we have a gas fire in the room we sit in in the evening.
Both (i.e. the whole system) need upgrading to make more efficient use of the gas though.
A

I know a few people who've retrofitted UFH to an existing gas boiler (for an extension). The have achieved this by fitting a manifold under the boiler. Any modifications to a central heating system should be made with the fact your boiler will likely be swapped for an ASHP at some point.