I recently sold my classic Mini on Gumtree, had the few usual idiots, but found a genuine buyer after 2 weeks.
Other free advertising sites worth trying are https://www.classiccarsforsale.co.uk/ , https://classics.honestjohn.co.uk/ the enquiries I had from them were genuine.
Also worth advertising on here with photo's, its the 1st. place I'd look if I was looking for a Puma.
Agree on the price, just sit tight and wait.
Good luck