In my Performance I'd be confident I could do that in winter, though I don't like my car to be like a sauna! I'd say with the heat pump in the new models plus going LR you would easily do it, could you not charge overnight at the in-laws, even using 3 pin granny charger to be belt and braces?
Not going to be possible to granny charge unfortunately, so looks like the answer is to be very light on the right pedal and will probably be fine. Time will tell - have a test drive on Monday 30th to make my mid up 100%, but currently almost convinced!