Cheers dav. No point in flying off the handle with these things and I figured I try and get answers from VM themselves before deciding where to go next.
This evening, I have yet to see better than 14.Mbit (according to the zdnet speed tester) but just now on speedtest.net I hit 3.6Mbit, which isn't bad in the normal run of things. Mind you, I did download a bag load of stuff earlier but stopped at 700mb just in case. I may well try and run some empirical tests later in the week, do 5 tests on speedtest and average the results then download some sort of large files off bit torrent (entirely legal ones, of course) and then run the speed tests again to see if the shaping has been switched on yet.
If lots of folks do this with a range of packages (i.e. 4Mbit 10/20 etc) and post their results and locations we might get a better picture of where it is and isn't happening at the minute as even VM themselves seem a bit hazy on that question.