There is different standard when buying from a company / car dealer and a private person. My guess is that you ascertained to a reasonable level that he vechicle is damp free. Private seller cannot be expected to get out fancy equipment and check everything - in that case you wouldn't be able to make any statement about the condition of the vechicle.
Funny you should mention 'pikeys' few years ago in Germany my uncle was selling his Mercedes to them - when he went into the bank to pay the money in (our recommendation to see whether notes are ok - one of them poured some engine oil into the cooling system. Later he opens the hood (after the deal was done, and everything signed) and tells us that engine is f*cked and he wants 1000 Euro off - and all of his mates surrounded my uncle. I convinced them to go to the local garage to check it out - when they were told by the mechanic that they poured the fresh oil into the coolant they asked whether they can get 50 euros for the petrol - all they got was my middle finger.
P.S.
People with caravans are evil.
Funny you should mention 'pikeys' few years ago in Germany my uncle was selling his Mercedes to them - when he went into the bank to pay the money in (our recommendation to see whether notes are ok - one of them poured some engine oil into the cooling system. Later he opens the hood (after the deal was done, and everything signed) and tells us that engine is f*cked and he wants 1000 Euro off - and all of his mates surrounded my uncle. I convinced them to go to the local garage to check it out - when they were told by the mechanic that they poured the fresh oil into the coolant they asked whether they can get 50 euros for the petrol - all they got was my middle finger.
P.S.
People with caravans are evil.