There are 2 parts to your question (1) changing the Entry on the Land Register and the Revenue, and (2) re-mortgage. To change the Entry, Forms TR1 and AP 1 must be submitted, and these can be printed off from this link
http://www.landreg.gov.uk/publicati ons/?pubtype=1 . The Revenue require submission of Form SD 60 which can be obtained from 0845 3021472. The approval of your new lender is required, which is usually by them endorsing Form TR 1. You will presumably hold the property in joint tenancy, which is where one of you pegs it the property goes to the survivor without wills, probate, IHT etc. The LR fee is �40, there is no Stamp Duty or other tax to pay except the VAT on any solicitors bills. Regarding re-mortgage, it is entirely up to you, your fiancee and the new lender as to who takes on the responsibility for the debt. From recent correspondence with me here on AB it seems that some re-mortgagors solicitors also insist upon also doing any change of Entry on the LR, so talk to your re-mortgagor about this before going further. I understand that a total "re-registration" fee of about �200 + Vat is charged (which includes all matters with the re-mortgage and with the name change). If your re-mortgagor will allow you to do it yourself and you need help with the forms, start a new question headed "Maud" and I will work through the detail of the forms with you.