I finally got my 50Mb working on Thursday and
www.speedtest.net showed 50.4Mb on it's London server - all others showed lower.
As of yesterday The London server has been showing 22-28Mb so I wasn't happy.
Having read this thread I tried downloading some of the Game Demos and got:
Adding up the speeds of the 5 files I was downloading consecutively was giving me a steady speed of 6.52Mb/Sec - which works out at 52.16Meg
I'm happy with that