First of all you cannot get blood out of a stone so anybody considering action should check the financial status on CG before throwing more money at this
Second it should cost closer to €6k-€8k to take the developer to Court to recover money
Next you need to ask Fusters how they inted to recived the money, the exact breakdown of cists and timetable and if they have suceeded with anybody else on the development
One a couple of people worth speaking are featured on this forum Lawbird and Maria Del Castro of Costa Azul Lawyers, click on link on left