Hi,
thanks for the link, very helpful :)
I used the North Circular and actually got there an hour early lol (however I know its one of those things that if i was to leave 30mins later i would be 2 hours late!! so hour in the gym before starting sounds good to me :)
I used it on the way back too and hit that bottle neck which did slow things down a bit, i'll try the m25 home tomorrow!
Alan