Firstly, don't feel as if you've lost out in some way. You totally haven't. If he'd stayed with you you can guarantee he would have kept his cash for himself anyway. He's clearly that type. He would have still been sponging and dragging you down but probably just with big promises of how he was going to take you on the trip of a lifetime blah blah. Basically you'd still be wasting your time, but you wouldn't know it.
Secondly - £220K is only a life changing amount of money for a sensible person, sadly - the kind who immediately invests it, buys a hosue, etc. There's no way he's going to make that money work for him
- no, it will be gone in a year or so, with nothing to show for it except a big car and a massive tv and some very expensive sky packages, season tickets etc. He may well have other big debts that he has to pay off now too. Again - you haven't lost.
This is a massively good thing to happen FOR YOU. This loser could have sponged off you for years. He clearly thought he was on to a good thing, he would have stayed and kept his head down and kept taking, if this hadn't happened. Thank god - this has shone a light, he's showed his colours and you're free. I'd be doing a jig.
You would never have been repaid willingly and you would have lost even more without this.
If you have the energy, you could indeed craft a little letter telling him that you've spoken to a solicitor friend and it seems that you would have a claim on a portion of his winnings as you loaned him the money which very likely went on the ticket. Tell him that it seems like it's the kind of case that you can get a no-win-no-fee deal on, so he either pays you back (count it up)££ now, or you'll go for it and claim a portion which you're likely to get, solicitor says £10k is probably a reasonable sum as it's a small portion of the winnings. Up to him. He might just pay you say £2k while he feels flush just to get rid, which would be something.
Oh and obviously in 18 months when you get the sad email telling you all about how his friends used him and all his money is gone - DELETE.