I'll probably spend the winter down in southern Portugal/Spain where temperatures are around 15 degrees in average during the winter. I've also installed an old heating that works with Diesel and electricity. But yes, summer life is easy and I'm looking forward to experience my first winter in the van.
BTW: I bought the van in February and already worked and slept in the van while it was freezing cold: https://ruby-on-wheels.github.io/blog/the-first-ride/ it was ok.