A group of 4 of us went for my sister's birthday. I would definitely recommend.
The only reason I have rated staff as just ok is because the staff member on reception that day was not particularly welcoming, she was quite abrupt. The staff inside the spa itself were great. I had the lava shell massage by Jade (I think!) the massage was great as was Jade. We had the afternoon tea which finished our day off nicely. We will be going back again.
Using public transport I didnt route plan. I got to T5 only to find it was a £5 bus journey away. This was not only additonal expense but it made us late for our experience. The staff were aware this was a constant issue but acted like a broken record stating that the postcode shows that its not at T5.