Take your time here, there is a lot to take in. I was told they drain and clean the baths a couple of times a year, after which you can see the bottom, otherwise the usual murky waters could not disappoint this intriguing site.
I booked the Torchlight Dinner package, and you can give that a miss. If you are at the Baths at dusk the torches are lit around the roman bath, a lovely sight to behold, but it has nothing to do with dinner, which is served at The Kitchen across the forecourt from the Baths.
I somehow got the impression the Torchlight dinner was served at The Baths, by Torchlight. That would have been lovely, and there is a restaurant, The Pump Room upstairs, which has views of the baths from some tables and a beautiful ambiance. Oh well.