Sadly the JEC Energy specialist disagrees with this "The other option was an Air Source heat pump, again not sure what size would fit until a full survey / design is done probably with a Vaillant Arotherm plus so rads would not change, only issue with this is the max running current cannot be more than 28.1Amps for your single phase supply, which includes Heat pump and bore hole pump." This is with a 100 amp, single phase supply. Maybe second opinion required.
My EV charger pulls 32 Amps, for up to 10 hours at a time. The SSE Engineer said that on each phase, with a 100A fuse, there is a limit to the number of 32A drawing units possible. So perhaps others on your supply loop have some high draw appliances, such as heat pumps and EV chargers, or pool heaters...
