Or, to put it another way, Step 1 is to obtain an Estate Agents valuation and agree it together Step 2 is to understand that the valuation is an asking price and that it might be sold for 5% less, so agree a discount Step 3 is to deduct the mortgage and all other costs Step 4 is to divide the surplus by 4 and round it off up or down.
Now, because there is a mortgage you must tell the lender what you are about and seek their consent. There is no other way, and the lender is not bound to agree. The lender will call it "Transfer of Equity". If they consent then because of legal reasons which I will not go into here the lender may require both of you to appoint seperate solicitors. If so, it must be accepted. Cost ? The lender will charge between �200 and �800 pounds, depending on your luck, and the seperate so;icitors if required about �250 each.