It would be rare for the mortgage company to withdraw unless there was something significantly wrong with the transaction.
If anything changes that is relevant it is best to inform them to avoid any problems.
In the Mortgage offer you will probably find a clause saying that they can withdraw their offer at any time, so yes they could do. However at this stage they have had all the info they require regarding your financial status, property valuation etc. I have never known it happen.
I suppose they would withdraw a mortgage offer if the results of surveys arent up to scratch
I had one downgraded ( 1985) where the morgage co said
£50k and not £60k so I rang the estate agent to ask for a lower price or else I couldnt continue and he said ( he later went bankrupt ) Oh that doesnt matter you have £10k in your deposit account !!
I said you are not meant to know that !
Yup Alliance and Leics that was had given him the info ! !
O those were the days !