How bizarre , I just returned (OK well got back on Wednesday) from the reverse trip to yours
I went to Swansea to visit some friends and go to a wedding. The drive from where I live to St Malo and from Portsmouth (after the nightmarishly long ferry crossing) to Swansea is approx 500miles. Now, I suffer with a dodgey knee and dodgey back and so the trip was never going to be comfortable but...
Thanks to a post here (I think by Simon) I put the seat heater on 3 and my back was fine, wish I could say the same for my knee lol.
Round trip with mostly motorway driving at 70mph on cruise control, a good 100miles of local driving in Swansea area (some quite spirited
) was approx 1200miles and I achieved an economy of 40.1mpg according to the trip computer
Thanks to the seat heater my back was 100% after the trip (and 3 nights sleep on mates sofa) and the whole experience was enjoyed. Well done Alfa , great car to drive on a cruise.
Now all I need to do is find a position for my seat that give my leg (with the bad knee) room to stretch whilst driving without having my arms 'locked' in order to reach the steering wheel. Either that or a 'gadget' to look after my knee the same way the seat heater did for my back.