are you south east then? i'm in Gloucestershire and the nearest one is 5 miles from me, i am so lucky!
I used it once a week for three months. jan- march 2012. It is a wee bit boring, doing half marathons on a treadmill. but it means you can still run, and running pain free is a massive buzz. i found it a massive confidence booster, running but minus niggles. its also helped me get quicker, as it taught me to turn my legs over quicker. easier said than done when you much prefer a plod (0: i am a 10k 60 mins kinda girl. and i was doing 14k in 65 mins by the end. i started at 50% body weight (because of the ankle) and at the end of the three months i was on the alterg at 85% body weight.
i havent used aqua running. my pool is pretty busy!