I am coming to the conclusion that despite my site having mains gas I’m going to go the ASHP route for UFH and DHW. This is primarily driven by the seeming faff of installing a gas boiler in the basement plant room - flue routing is a nightmare in our instance. Likely I’ll want to add solar PV at some point in the future too which I understand can be more advantageous in an ASHP system.    However,  for aesthetic reasons I’d like to hide the ASHP somewhere - the house is built into a b