You should offer the collection to a freelancer, of cause he only gets paid, when the money is delivered to you! It's very easy done and can be effective on con artists, that really do want to avoid any publicity.
You may also want to do a credit check on him or dig up some crap and leave it on his doorstep, these types can be handled without any violence if you choose your words carefully....just like any other chess game, strategy is key, but don't get yourself in trouble over it.
Also depends in which Country he is too! His car is looking good is it, that could be changed, the paintwork i mean name and shame is the way. I would also be more than irked I'm afraid.
Although when I was crop spraying for an ex Army Officer, I had a contract that he paid my digs up in Scotland for the whole season, though i finished the work in 3 months, of a 6 month contract and he needed to relocate me to nother area which we had already discussed before the contract was signed, he refusing to hold up the contract, which was costing me a great deal of money keeping the
property on.....
In which case i had to pay the rental myself, with no income because i was on a freelance basis and relied on the contract fixed income plus bonus for work completed.
I was also irked so a gave everyone i met in the village free petrol at his expense has i had a Company petrol account
That put an end to our relationship, but who needs friends that only want to use you to make money for them! I know my net worth and I value my integrity, everyone would like a win win situation, it can only happen if you make it happen, otherwise you will be taken for a ride!
20K is a lot of money for some people, I would just pay him a visit and explain he's got to start clearing his debt, otherwise you will have to take alternative action.
I am still owed money in UK was 2000 pound, not much, but the guy had spent it without permission, i was overseas and his marriage broke up.
Though he is in a criminal environment and his hard core ego is his label in front of his mates, a regular in prison...
I know if i confront him in front of his friends, he would have to do something rather stupid to hold face, so I take him for a ride and calmly offer him the alternative of paying his debt, or i would have to physically hurt him, and i really didn't want that to happen.
Fear is king no matter where you are it must be faced, that is the only way to deal with bullies, and con artists.
Psychological warfare works, but you have to be confident to go the last mile too, just don't get caught having your pep talk!
Take splatted advice in the first round and take it from there, step up the pressure the second meeting
Make him an offer he can't understand? 
