It is not possible to enter into a legally binding surrogacy agreement in the UK. Nevertheless, it is always good advice to put an informal written surrogacy agreement in place to ensure everyone is clear about their expectations and all eventualities are considered and planned for. Do be aware that it is a criminal offence for lawyers (or anyone else who charges a fee) to ‘negotiate’ a surrogacy agreement, and so any surrogacy agreement you put in place will be an informal document.
The non-profit surrogacy organisations will provide you with guidance and support with putting your agreement in place. There is also further information about what should go in a surrogacy agreement in the government’s surrogacy pathway document at
https://www.gov.uk/government/publications/having-a-child-through-surrogacy
Many intended parents and surrogates are concerned about what would happen if the other party changes their mind during the surrogacy process. This is incredibly rare, and very unlikely if your surrogacy arrangement is properly thought through and carefully set up. It is also not the case that the surrogate has a right to keep the baby if she changes her mind. Of the few cases in which the surrogate has sought to keep the baby after a surrogacy arrangement, the family court has decided who the child should live with on the basis of what is in their best interests. In practice the family court has been just as likely to award care to the intended parents as to the surrogate.