lost, I think, that like many things, there is a difference between the informed choices that a well fed, housed, educated woman in a western country can make, and those of poor women (both in the west and in other countries)
The Indian surrogate dorms are exploitation, yes, they're making an informed choice, but that choice is so heavily influenced by the probably lifechanging amounts of money (that will pay for their own children to be fed, housed, and educated) that I'm afraid I can't see it as a free choice.
Just look at the Indian attitude to poor people - poor women especially and tell me that you feel these women are truly making a choice without coercion?
Both women are making altruistic choices - the surrogate mother in the UK probably is doing it to bring happiness to the IPs, with any economic benefit as a side effect, but the woman in Thailand or India is doing it to give her family better prospects (although I'm sure she also is pleased that the baby is going to parents who want the baby so much)