catlady and all.
Yes, he contacted me again in a massively long email.
Again more legal bullshit but with one genuine legal point.
So he says he collaborated on the work which gave him joint copyright
..... I said sending me the photograph (copyright free) and suggest a colour scheme was not collaboration in the legal sense.
He said he also has 'intellectual property rights' as he had suggested how to do the work
........... I replied that's a lie as IPR applies to logos and 'original' ideas etc and painting old photos was not an original idea.
He said he has 'invested' in me by paying a nearly £100 for two earlier works that had been on similar lines and had taken many hours to complete and our 'understanding' was copyright would transfer to him
........I said he had paid for 2 saleable works he could print and recoup his costs. Also we did collaborate on one as he had a license for the photo and I gave him permission to reprint 10 copies and if he needed further contact me and we would discuss a price! 
He said we had a contract to supply the latest picture (above) and I was holding it hostage. I said true, we had a contract but as my computer had blown up due to a power surge I couldn't complete the contract and would not be charging him for it. As a gesture of goodwill I would waive the fees for a couple of minor photographic touch ups I'd done. Also at a later date I would download the photo again and repaint it and he could buy a print off Etsy.
Not heard a word since
. Short of suing me for breach of contract in America and getting a British court to enforce it (minimal chance) he is stuffed.
The ace up my sleeve is that there is a legal maxim of 'clean hands' which means you can't come to court having done something illegal in relationship to your claim. As it is in writing that he tried to extort the copyright from me using legal jargon he knew to be untrue, he doesn't have a cat in hells chance of succeeding.
Thank you google, MN, and judge Judy 