Car sale overseas - V5 - flunky
I have sold a car on ebay (old banger, £200) to a guy from Poland, who's taking it back to Poland on a car transporter.

Do I just mark it as 'permanent export' (section 11) says 'I declare that the vehicle will be exported on the date shown opposite.' It also says you should retain section 1-8 for the registration authorities in the exported-to country (i.e. Poland). But that would be in my name, not his.

Technically I have no way of verifying that, because I will have given the car to him.

I can't fill in, section 10 is for a sale to a UK-based new keeper.

What's the correct procedure?
Car sale overseas - V5 - Dave N
It's him that's exporting it, not you. So just fill it in with his name and address.
Car sale overseas - V5 - Collos25
If you do not know his name and address put "not known".