This is my response to your dvla query, which will not accept responses for some reason.
Well you should not have fallen for the one about him being a dealer – the dealer notifies dvla that they are a dealer, then the extra owner does not show up on the log-book.
Things could be worse, he could have racked up all sorts of offences (fines) – for which you would be liable.
Contact dvla asap and explain the situation – make sure that they record the fact that you are no longer the registered owner/keeper.
With regards parking charges in a non-EU country, I think they would be lucky to be able to enforce such a fine – even if it genuinely was you who parked the car.
I have heard that some of these collection agencies can get nasty with their threats – but in the end they must take you to court to get their money. You could write to them and explain the situation – but most of these operations are only after money and will not take no for an answer.
Alternatively you could pay them the £90 and think to yourself - I got away lightly for being so stupid.