Who advised you that a personal debt could not become a charge on the property? I know it can be, because I've done it, but that was by agreement with the other party.
Even if he didn't agree you could presumably have gone down the route of going to Court and getting a CCJ. If he then did not comply with the Court ruling you could have asked the Court for a charging order.
If a solicitor was involved and did not fully advise you on this, you might possibly have a claim against them.
However, unless you can find out he has bought another house the charging order route is now closed to you, but you could still go to Court for a CCJ and ask the Court to order payment forthwith as you know he has just sold a house. Your problem may be finding him, if you don't know where he is now living.
The solicitor you are using should be able to advise you on all this, or you could try the local CAB.