only your lawer or marbella town hall can tell you if the compex has a LFO or not.but i would have assumed that you would have been asked to complete if there was one. some people decided to complete without the LFO and paid the full price of the property. this was ther choice as it was yours too, but if no LFO is ever issued they can never legally sell their property or get water/electric in there name and run the risk of fadesa turning off the water/electric, as just happened, fortunatley the town hall intervened. as for you prefering a different unit in your complex.
You, (WE) are not exactly in a bargaining position here, i understand your concerns wanting a different unit in your complex(FOR WHICH YOU WILL NEED A LAWYER) but you might be better off taking the agreed apartment instead of chasing a % of your money back. remember
if you want out of the contract you must sue before any LFO is issued.
ps you might consider speaking to a new lawyer.
good luck anyways.