Hi all, thanks a lot for the replies, very helpful.
It was indeed the same controller on the same frequency. I'll happily admit that I have very little idea of what goes on in the ATC side of things so I'm in no way having a go at the controller here.
What we took from his original clearance was that at FL150 he wanted us at 220kts so (possibly wrongly as it wasn't an actual clearance) we assumed the speed restriction applied to this flight level as opposed to the level flight aspect. In the past where this has happened there is normally a clearance of, "now cleared FL80, on passing FL150 speed 220kts" but on this occasion we didn't receive that. Again, busy airspace and the controller was having to work hard so it's understandable that a small omission like this may slip in.
5milesbaby: It's interesting the point you make about the pilot not passing you the exact clearance as I've flown with people who on initial contact will state "we've been given a speed of 220kts" whilst we're still at 280, and as someone said earlier, losing those 60kts can take time, especially if you've been distracted by the headlines and are coming in a bit hot! (That's a figure of speech by the way! There's no tray on my a/c and the control column gets in the way of reading the paper!) I'll make sure that we always make our speed and restrictions clearer in future.