I have sold a car as spares or repair via eBay, a trader has brought it, I listed all that I was aware was wrong, had an mot done on car 4 days prior to placing advert and had repairs done to pass mot. Trader was told also what was wrong and what was happening and he was still happy to drive it away from leicester to birmingham. He is now saying he wants to return it and have his cash back, receipt says like advert, spares or repair, sold as seen with no returns policy.

As long as it was advertised as spares or repair and sold as seen he has no recourse.

Why does he want to return it ?

Because he says head gasket has gone, but he did drive it to birmingham,

... had an mot done on car 4 days prior to placing advert...

What is a "mot"?

AK - MOT is a Ministry of Transport vehicle test, a UK requirement.

As it was sold as spares or repair that could easily come under that heading.
He has no recourse through eBay as he paid cash.

Issue of international sites, when they said Birmingham I was thinking US, ( Alabama)

But if it was advertised as parts, and if the receipt said parts, just tell them NO and don't talk to them further about it