Sale of goods act does not apply to private sellers - simple as that. It is down to the buyer to make sure goods are as described before buying.
Paypal offers no protection on gifted money (which is why using it for sales is a f**king stupid idea) it's not designed to be and never will be - greedy sellers that demand gifted funds deserve all the grief they get (but that's another thread
He has no claim but tell him that you are willing to let him have his day in court but will be claiming loss of earnings, travelling expenses etc when his case is thrown out. Also ask for a report from an independent engineer(tell him you expect the items to be made available to your engineer for inspection) and his solicitor's name and address.
My guess is that he will just go away
