"Yes", we too used Ambasun International, and "Yes" we too did not have a bank guarantee !
I suggest you go down the same route as us, if you're able to afford it that is ?
Our original Spanish lawyer cancelled our contract, charged us a small fortune, and did little else !!
We are now with Costaluz Lawyers ( Maria Luisa De Castro ), who is commencing legal action against the banks, for many clients that are in the same position.
She has already won a number of cases using this method, and got the full deposits back, along with costs and interest.
Yes, we had to pay a large amount of money up front ( we obtained a bank loan ), but, we feel this is our last and only shot at getting our money back, and are confident that Maria and her team will be successful, as she has been with the others !!
Barry & Sue