I’ve just received my 10% deposit plus interest back (minus the lawyer costs)!
Like you, I was frustrated with the poor communication from the developer and what action to take.
My lawyer (from Lawyers of Spain), took action [litigation letter] to recover my deposit directly with the insurance company
who issued the bankers guarantee. Their litigation partner visited the development site with a surveyor to assess the amount of
time required to finish the development.
I hope this helps.