Separation v Divorce and property.

Hi. So I remarried a number of years ago and my spouse came to live with me in England in 2009. In 2011 I bought a house and used all my life savings of 30k as a deposit. Now the marriage has gone into rocky waters. She hasn't contributed a single penny to the house, and isn't on the mortgage or title deeds. If things went pear shaped could she still have a claim on the house? We have been married 12 years.
I don't mind paying her, but I feel that she is trying to get away with whatever she can
Ideally I want to sell the house and then give her some money, ie money she can use to get her own place etc.
But someone told me I can't even sell the property if she doesn't consent. I was told there is now a form that has to be filled in by anyone over 18 who lives in the house.
Is this accurate? (even when she not on the title deeds or mortgage? )
Lastly I wish to know what would happen if I paid the remaining mortgage of and then 'gifted' the house to my children from 1st marriage ie could she put a stop to that. Any help would be appreciated. Thanks