autopilot_off: was it the same controller that cleared you below FL150 that had given the original instruction? If so then they should have reiterated the speed clearance (or just said "fly speed 220kts" as they gave you the descent through FL150 if you were nearly there).
However, if there was a frequency change then what did you report on first contact exactly? I had a situation once where this exact instruction was issued but then on contact with the new frequency it was reported as "descending FL150 by TIGER, 220kts". They were given FL80 before leveling and they didn't come back to 220kts and lost separation with the jet in front. The pilot was blamed for not passing on the EXACT clearance to the next controller and for making a false statement when they said they were doing 220kts to the next controller.
BGQ - all UK controllers know that a new clearance cancels the previous so if they still required the level restriction, they should have reiterated it. We don't like it but its a very black and white ruling.