Your partner will also have to sign something to give permission to come off the mortgage - and some lender's require the person coming off the mortgage to get independent legal advice.
I bought my house 8 years ago. I then met him and 4 years ago we remortgaged and put him on the mortgage. The equity until that date is mine and we will split any equity after that date. At the moment we are not living together but he is paying the mortgage. I'm looking at my options and what I can do regarding the house because I don't want to move. I also don't think he would make me move. He is a very nice decent man and would put me and my children before any financial gain.