Making progress we are but have a couple of questions.
Can we install the fill / flush valve: outside by the heat pump, much easier to get at if we can, just needs good insulation around it and I guess I will still need a filling loop inside to pressurise the cicuit.
Each of the UFH loops have a control valve at the bottom and flow meter at the top which way do the control valves work, unscrew to open or screw down to open. The rep from the company did not know but their technical guy has yet to get back to me, thought there is bound to be an expert here somewhere.
Do I need Non return valves (NRVs) in the return circuits, UFH and Cylinder, before they re-join to go back to the Heat Pump, I can't see why I would but I saw somewhere doing it.