I don't understand your question.
If the house has never been lived in, how do you know there is a mortgage on it? Even if you did know the o/s mortgage, how would you know it has not been partially paid off in a lump sum, over what term the mortgage was taken out or how much was taken out initially etc etc. The o/s mortgage is completely irrelevant.
If there is a mortgage, the lender cannot give you information (unless you actually own the house). The lender can't force a sale on your behalf. If the house has been repossessed, the auctioneer is selling under the lender's instructions.
Did you mean you would like to find out whose name is on the title deeds i.e. the owner's name? If so try the Land Registry.