Firstly - apologies for not posting this before now. I've been running around like a blue arsed chicken and I forgot all about this.
I informed the customer that there was a high probability that there had been piston/valve contact and quoted him accordingly. After he had recovered from his triple bypass he decided that, as the vehicle was due to be changed, he would sell it 'as is'! He sent a recovery truck for it and I invoiced him for the work I'd done so far. Everyone's a winner!