An explanation of why a heat pump isn't needed in the UK is provided by @Miles Roberts CG in the November podcast at 24:48.
I think there are two different heatpumps. The one for cabin air is usually an air to air heatpump while the one for the battery pack is an air to liquid one i guess. Im not 100% on this, i know ive read about it in the past but the details escape me.I thought the heat pump was primarily to heat the battery as well as the cabin.