I have a small lightweight folding chair and it didn’t lay flat in the Hyundai Kona. I don’t know if the Bayon is any larger? Is the Kia Stonic the sister car does anyone know?
The Renault Captur and Citroen C3 Aircross might work?
All cars mentioned are below your budget.
There are a handful of BEV cars that might work for you as well. The Nissan Leaf, Renault Zoe (boot might be too small), Vauxhall Mokka E, Kona EV (smallish boot), Citroen eC4 and the MG ZS. Again, all under £1k.
Best of luck.
Skoda Enyaq Race Blue