This doesn't end well for anyone and I can't see why anyone would think this was a good idea but with more and more informal arrangements for surrogacy (this is formally an adoption so I don't know why the woman is called the 'intended parent') I can see this sort of legal battle becoming more common, maybe even in the U.K. where law reform is proposed.
The situation is, a woman posts on FB
“[W]ho wants to pop out a baby for my [fiancée] and I?!”
A mother of two offers herself and gets pregnant with her own boyfriend, so the woman and the fiancée asking have no genetic connection to the child (as would be required for a parental order in the U.K.).
The two women never meet in person.
Later the mother changes her mind but the baby, once born, is handed over to the woman, due to a judge ruling.
A legal battle ensues and it involves a brick through a window and I imagine a confused little 3 year old boy and a lot of heartache and expensive lawyers for everyone involved, apart from maybe the fiancée who is no longer in the picture, who has no relationship with the boy, genetic or otherwise.
As no money appears to change hands it isn't 'selling babies on the internet' but from the outset no one seems to be taking it all that seriously and no one is thinking about the little boy, who has two full or half siblings and a mother who he doesn't live with and who wants to have him with her.
https://nypost.com/2021/09/23/woman-locked-in-court-battle-with-surrogate-she-found-on-facebook/