Spa at Ageas Bowl pictures: (eForea spa which is also at Bournemouth but differing in features and scale):
Hope these pictures give a sense of the great spa facilities here. I didn't get a picture of the outdoor terrace or outdoor whirlpool as there were several young ladies enjoying it at the time...
Free for diamond member only (not sure about Golds...) £ 10 for guests of diamond member. Not sure about non-resident prices or massages, treatments, etc...
There are also some sitting areas to chat and have a drink or read in the spa in other rooms but I didn't use them so don't have pics of those sorry.
Obviously, separate changing rooms for men/women. Spa areas are mixed gender areas with no separate facilities I was aware of.
First the general look and space of the spa:
The view you get coming out of the change rooms:

view from entrance into spar area by
BA_pics, on Flickr
View once around the corner of the first spa section: (the outdoor area is at the other end through the doors)

view of remaining indoor spa area by
BA_pics, on Flickr
Pics of the various areas:
Main feature: (hydrotherapy pool with various jets located around it with indoor whirlpool...all quite warm water):

hydrotherapy pool wtih jets by
BA_pics, on Flickr
2 Steam rooms: (different scents in each of course)

steam bath 1 by
BA_pics, on Flickr

steam bath 2 by
BA_pics, on Flickr
Very large sauna with nearly floor to ceiling window out to main area and seating around 15 max (IMO):

sauna by
BA_pics, on Flickr

large window of sauna by
BA_pics, on Flickr
opposite the sauna is a sunbed area with heated, tiled sunbeds to relax on, very warm and quiet...

heated tiled sunbeds by
BA_pics, on Flickr
There is a footpath area for two people:

foot bath area by
BA_pics, on Flickr
There are several showers around the walls, most standard type arrangement but one with a rainforest warm shower and an ice blast setting...try to keep your mouth closed using that one (they take a few seconds to adjust the temperature before spraying)...also an ice bucket and straight ice for those so inclined:

hot cold shower by
BA_pics, on Flickr

ice anyone? by
BA_pics, on Flickr
The changing room itself: (quite large with full washroom facilities, showers, vanity desks, sinks, lockers (number code to secure):

change room by
BA_pics, on Flickr

lockers by
BA_pics, on Flickr
Highly enjoy using these spas where time allows. Weekends seem to be busier from my limited use so far. Weekday evenings are quite peaceful and quiet.
Staff are all very welcoming and friendly, a real pleasure to talk and deal with. ^
Hope these are of interest, try them out if you happen to be staying in one of the newer hiltons...