Thank you for your help, everyone. Yes, everything points to quinces,
and I have double checked on Google for pics; though how I came to
buy the tree as a 'persimmon' I'll never know!
I'm glad to know the fruit is edible if cooked, because the only time
I bit one I hated it --- oddly the flowers don't have a particularly
nice aroma either.
Too late for this year --- yesterday I had to strip the tree and throw
away the fuit because my annual visitor, a very fat black bear, spent
the night in my garden causing havoc and pooping prolifically. Last
year he ripped off one big branch.