Hello Matthew
I am also struggling with the 9kW Daikin Monobloc, out of interest who did you contact at Daikin to get support on an engineer visit to assess the HP suitability? Mine was installed by a company other than Octopus, where others have had success like yourself for a swap, so I am hoping to engage Daikin directly as they were the ones who referred me to the installer as they are in their installer network.
Many thanks for any advice you can send my way.