Presumably you can go with a different mortgage provider, but is it worth the hassle at this stage? Also, the fact that you are paying X and need to borrow X is really all that is relevant at this stage, i.e. I don't think the LTV will be assessed on X/X+20%
i.e. you have apartment for €300,000. You have applied for a mortgage for €300,000. In the past three months, a second phase has gone on sale with the same apartments selling at €350,000. You still need to borrow €300,000, which is still 100% of the original purchase price. As far as I am concerned, this does not mean that you can qualify for a lower LTV (i.e. purchase price of €300,000/€350,000) at this stage. But I'm open to correction on that.