>>> "Many other models of monobloc ASHP do not use an 'indoor unit' to collect these bits together... if that helps make the job simpler or less disruptive?"

Simpler or less disruptive because you don't need an indoor unit eg look at Samsung or Daikin monobloc . Everything in the outdoors unit, apart from the TS bits you already have, so no expensive pipe, or breaking out the kitchen floor. You're in the best place to choose though!


>>>" strange oxymoron with their system.."

Systems with 'indoor units' like this are often sold by gas boiler brands, aimed at builders or gas fitters who are familiar with "Y plan" gas heating and want something indoors that looks similar with all the components pre-assembled in it. They don't want to do plumbing or F-gas work on site, because of the skills shortage in those trades.

Y-plan is not such a good fit for a TS set up, EG the HP would ideally like to control the different temperatures in the TS, and the secondary circ pump to move the stored heat from the TS to the UFH at the right time. It would prefer to generate cooler water for CH than for HW, using its own weather compensation.

A more HP-specialised manufacturer (one of the air conditioning brand names) might expect the installer to design these plumbing systems to fit each site/client and get the best out of the HP, by analysing heat demands and pipe resistances. The resulting higher CoP figures will reduce the energy bills. Those skills are less available though.

The "Heat Geek" website run training courses for installers, and also started training courses for home owners who find themselves in John's position of having to do their own design work.