Lads,
Many of the posters here clearly don't have a clue how the conveyancing system works.
To the OP - you do have contracts. You signed them when you paid over your 10%. This binds you to purchase the house, and binds the builder to sell it to you and do his work, assuming you comply with the conditions.
There is no such thing as "final contracts". There is only one set of contracts, which are already exchanged.
The last step is called "completion". This is where you pay over the balance and the builder gives you your title documents. It sounds to me like this has also taken place.
Personally, if I had been your solicitor I would have retained a significant portion of the balance until all snags were done.
OP I think you have misunderstood some of what your solicitor told you. I think, rather than worrying about it, you should simply call her/him and arrange a meeting so that you can get a copy of your contracts and ask all the questions that are on your mind. these are the questions I suggest you ask:
1) Does your solicitors have your title docs and are they all in order?
2) Has any money been held back?
3) Did the builder given any special undertaking to complete snagging, over and above what it says in Building Contract?
4) If monies have been held back, ask your solicitor to write a letter to builder saying that, if they don't sort the problem in 7 days, you will use monies to retain your own contractor to complete the work.
Good luck.
Kate.