Bank vals are based on a euro per square metre basis, dependant on location, build quality and not much else! Various variables due to interior size, terrace size remainder of garden plot size, if there is a garage and its size, sotreroom….I could go on and on. However, market forces are such that people have to sell for less than bank val, so it becomes irrelevant. Many are selling under the bank val now.
So, the purchase price is 125k and your costs are based on that, ie transfer/purchase tax of 7% is based on 125k etc.
Your lawyer can and should advise you further – you are paying him for that!