While testing a large percentage of cars on offer through the scheme during 2019 as I could order from October 19 I have to say that the most comfortable by a country mile was the Citroen C5 Aircross for both ride comfort and seating, it was the most comfortable I have been in years and not just in a car but seated in general, had a long test drive and spent 90 minutes stuck in a traffic jam on the M1(my crappy luck) and it was wonderful, it was saddening that I couldn’t fit my larger powerchair in the boot otherwise it would have been what I ordered.
The best of the rest were mostly Citroens and Peugeots with the Volvo XC40 high up on the list(all based on comfort)
I ended up going for a Peugeot but passing on the leather as I never want that again but the seats are super comfy and the ride sublime, might be worth a look.