Quick update. The police finally came round to see me this week (I reported the scam in January).
I gave them all the details - screenshots of my Facebook chat with Mr Smethurst, PayPal payment notification. He had just posted more scam items on marketplace so I showed them that too before reporting him again. I also gave them the address of this thread and the details I’ve gleaned from here.
They thanked me for all this but basically said there is very little chance of stopping him.
1. Facebook are apparently very arsey about handing over user data to the police so very hard to get much even with an account name and address.
2. I live in Scotland and apparently cross-border cooperation between Scottish and English police is abysmal- English police aren’t interested unless basically the Scottish force has got rock solid evidence to convict.
Before they left one of them told me that if you want to commit a crime and get away with it then this type of fraud is perfect.