Compensation for Spanish properties bought off-plan

I have paid a deposit on a flat at planning stage. When I paid the deposit I was given the plans for the flat in which the total living space measured 74m2 and cost 120,000 euros. However, when it came to signing the sales contract the promoter told me that the main staircase had to be moved which affects 6m2 of the total metres in the flat which means that the flat now measures less. The promoter has offered to discount 6000 euros from the total price but according to my calculations these metres are worth more than 6000 euros. Do I have the right to ask for a larger discount having already paid a deposit or do I have to accept the discount of 6000 euros offered by the promoter?

Answer:

You are right that the discount is less than the actual calculated value. According to my figures the discount should be approximately 9000 euros.
You can refuse to sign the sales contract but you need to evaluate whether the 3000 euros are worth taking out a claim against the promoter. You also have to evaluate the value of the flat given that a new flat would now cost more than the price originally agreed with the promoter.