The husband, the wife, the surrogate and her lesbian lover

I am toying with the idea of turning my surrogacy TV thriller script  'Misconception' into a novel. But first I have to contemplate re-working the script as a potential two-part television drama.
Because the law appears to have changed with regard to surrogacy (and this is only the foundation stone of the story) I have been consulting legal speciaiists to clarify what happens to a couple if the husband is seduced by the surrogate. The wife appears to have no rights whatsoever if the husband and the surrogate decide to claim the baby as theirs.
What isn't clear is what the situation would be if later in the story the surrogate's lesbian partner turns up - maybe married, maybe not.
There is a spoiler here in that I am not revealing the meat of the thriller action but if anyone out there has a view on what everyone's status would be in this unusual ménage a trois do let me know.