Hello. I've swum there lots in the past. There are good changing facilities available with hot showers. I think the session is 8.00-9.15. The organisers get there about ten to eight and unlock the changing block.
Once they've unlocked, take your things into the changing block and get into your wetsuit (don't forget your flip flops). Go back to the car and put your bag away then give your key and your money (£5 last year) to the life guard. The lifeguard sits at a picnic table next to the pontoon. They will take a list of names as people pay and they'll cross you off the list as you come out of the water. Everyone mills around at the edge of the lake waiting to be allowed to get in the water. Most people are triathletes in wetsuits but you get a few hardy souls in costumes - lots of nervous first timers feeling self conscious and a few hard as nails ironfolk.
While that's going on, the other lifeguard goes out in the boat and makes sure the bouys are in the right place. The loop is roughly 400m - lopsided square. It's marked with big bouys (but it's easier to sight off the trees and buildings as they are bigger). Once the boat is in position in the middle of the course they'll let you start swimming, and off you go. Some people go round and round non stop. Others do one loop and get out. Others have a break and go round again - you ge the picture. Sometimes newbies splash around by the pontoon to get the hang of it before going out to the proper loop.
It's very friendly. The water is cold and clean. There's a cafe on the other side of the road about 100m up the road (towards the A419).
Edited: 13/05/2012 at 16:30