I apologise for the delay in getting back to you. Blame weekend. I will be off-line now until later.
If you add your partner to the deeds of your house, the lender is probably going to insist that your partner is also added to the mortgage. That would give your partner liability for the full mortgage along with you.
If he puts nothing into the property and there is no agreement as to what will happen when the property is eventually sold, then the proceeds are split 50-50. If you therefore want to preserve your equity, you need a deed of trust to reflect your individual shares and preferably a cohabitation agreement to prevent him claiming an equitable share by virtue of any money which he alleges he has paid the house.
I know you didn’t ask about any of that but it’s worth mentioning in case you haven’t thought about it. Of course, you may not be bothered.
There may be stamp duty to pay on the transfer from 2 names to one name and that is based upon the amount of mortgage. If the mortgage is under £250,000, there is no stamp duty to pay. It is based upon half of the mortgage and half of that mortgage is under the stamp duty threshold.
It depends what you want to achieve by putting the property into joint names as to whether it is what you want to do. If you want to make sure that your partner gets your share of the house in the event that you die, then it can be done with a simple will.
If you can tell me what you’re looking to ultimately achieve, I can then tell you how to go about it.