If you do a site search for THG and the hospital group you should find lots of first hand stories from people's experiences. Also, search for WGA and why go abroad as this was their old package which most people seemed to use about 1-2years ago (which I think has been discontinued). Around then, there were a lot of negative stories, particularly about being sent down to the discharge lounge by 7am the day after surgery (not so much fun if you were late on the list for the op itself) and lack of aftercare/having to chase follow up appointments.
It does seem that they have sorted some of these issues, as I haven't seen any negative posts for a while, and certainly not the volume we were getting.
WLS group has always had good stories on here, particularly for their aftercare, I can only recall one negative one!