That can be made to work, but I’d need more info and to understand the way it’s been plumbed / pumped / operated etc to see if hydraulic separation needs to be considered in this conversion.
Assuming it’s just the OEM pump in the ASHP atm, and flow and return just tee off to UFH and rads?
Day job for a decent plumber, one who doesn’t spend longer talking about how it ‘can’t be done’ than the job would actually take to do.
This is a low temp pump and mixer set, one I’ve been fitting for nearly a decade. 1” BSP connections to match your manifold.
Link
This isn’t a typical, much cheaper, TMV, but instead a thermo couple type actuator which responds by temp / hydraulic in a far smoother and more refined way.
These don’t whine or chatter at their lowest settings like a regular TMV’s often do, so with this type of unit you’ll get very accurate, low temp control for the UFH in the slab.
Needs a bit of “tight space plumbing” skills, and prob to pack the manifold off the wall very slightly, but defo can be done in the room available.
Done these in much tighter spaces tbf!