Mortgage offers in Scotland

Glasgowborn

Hi there,
First post on MSE so sorry if this has been asked and answered previously..

I am currently buying a newbuild home in Scotland under the "help to buy" scheme

I have had my mortgage promise and mortgage offer approved months ago.
My "help to buy " was approved at the same time. And missives have been concluded we are just waiting on the property being finished as it's still not fully built yet. Some money has changed hands between myself/solicitors/builders ( £500 reservation and £1500 for the first stage of my deposit)

Now to my question... Having everything concluded such as missives and mortgage offers etc does the bank have a legal responsibility to give me the mortgage? As Scottish mortgages work differently.
I am just a bit paranoid that they offer can be revised or rejected even though I am legally bound to buy this house.

Any help is greatly appreciated