Thanks for your reply.
As there is a Mortgage on the property, I'm afraid you would need to obtain the Bank/Building Society's consent to have the house transferred to you.
This is because if the house is transferred to you, you then become legally responsible for paying the Mortgage.
They may or may not agree to this after considering your ability to pay the Mortgage/your age/income etc.
If this is not possible, they may well agree to have the property transferred into your joint names (on the basis that your son will remain as joint owner, they ar elikely to consent).
Of course, if your Son is able to raise sufficicient funds to pay off the Mortgage, once this has been cleared, he is free to transfer the property to you. This is done by instructing a Solicitor to prepare the necessary Land Registry Transfer document which is signed, and then registered at the Land Registry.
I hope this answers your question, and if so, I would be grateful if you could leave positive feedback.
However, if you require any further assistance, please let me know.