When you say they have you over a barrel, could you not consider changing your solicitor. Either way, you will have to pay legal fees but why pay Aldea ( presumably they were recommended to you ) when they were partly to blame for you being in this mess in the first place. If anything, they should be taking some responsibility.
We were really angry when our first solicitor ( recommended to us) asked us for fees up front to reclaim our money when he assured us that he had made all of the legal checks ' how can there be a problem ' he said.
You should not feel foolish, you simply bought a product that the company failed to deliver. Now, Huma should recognise that they have acted illegally by refusing refunds. We all have sought and received legal advice when buying our property at ACC. We trusted them to ensure that our purchases were legal and that our money would be guaranteed. So you are not foolish --- they are incompetent and have let us down. Now, they are quite happy to make even more money out of us -- if I were you I would not give Aldea any more of my money and would look somewhere else.
20K is a lot to loose, don't give up !!