My wife and I took out a joint mortgage before we were married when we were only living together. After we were married I phoned up our mortgage lender and asked them to change her name on the mortgage to her married name. They wanted �200 to do it, although to be fair they also said it was completely unnecessary as the name on the agreement was merely a means of identification and it wasn't important that she'd changed it by marriage since then. They advised us not to change it and so we didn't and it's still in her maiden name.
All of which is starting to go off topic. Point is that even just to change the name on the mortgage, supposing the lender is agreeable to a single person on the mortgage is likely to cost a significant fee.