Two courses of action can be arranged;
1. I'm not as tall (or as heavy
) as Hugh, but as an ex-powerlifter who can still deadlift 680lbs and has a 14lb sledgehammer in the van (don't ask
), we can be a pretty formidable pairing.
2. I also own a fully legal, target air rifle (with telescopic sights), which could be trained on the dealer's cars....
(both the above are true, and I would help out - honestly)
This post will self destruct in 5 seconds, 4..., 3..., 2..., 1...
On a more serious note, I doubt if you will see your money - I get the impression that this isn't the first instance of this happening, and you may find that quite a few palms have been greased.
You may wish to find out where this person lives and leave a few handfuls of nails scattered around his car (as you drive past, of course).
He can have his (your) £100, but it'll be at a high price to him.