Their website is
http://www.oxnat.org.uk/For you that would be a bit of a trek just for a swim! It is possible though, because it is in Didcot, which is on the mainline from london. I live near Oxford and have never been for the fact that I know many of the lifeguards who work at the pool! I would imagine it would be a great experience and it is a weekly event too!
I\'m glad that this has been useful for you.