under UK law by default the surrogate is considered the legal parent and surogacy agreements are not enforceable by the courts. If pressed there may be a custody hearing but again under uk law the person who gives birth is considered the legal mother so it would be an uphill battle to take the kid away given the legal status of the biological parents is "some guy who wants the kid".

basically in my country the surrogate pretty much has the right to first refusal on the kid unless the court would take away the kid anyway for welfare concerns