Yes... Give them a receipt stating sold as seen. No guarantee or warranty implied or given. Date it, sign it and get them to do the same. Photocopy it it and send it to yourself recorded delivery and don't open it. HTH.
Cheers chaps, thought it was, it's a mate that's bought one, it's broken a couple of days after and it's not the sort of problem that would just have happened overnight, but didn't think he'd have any come-back!