Hi Claire,
to answer your qeustion they do credit score in order to provide a mortgage in principle. It will now go to an underwriter who will asses outgoings, wage slips, bank statements etc. to make sure that they are sufficient. They will also asess the property i.e floor, area to see if its a high rise as some lenders may not lend on a certain amount of floors or if there is commercial property below them, or even if they are what they called over exposed in a certain area (meaning have a lot of mortgages already).
but I am certain that your credit check would of already been done. Good luck and hopefully it comes out well today for you.