divingduck
If held up on descent, as you indicated the 330 was, slowing down is the most appropriate thing to do. It is called energy management. If they were to maintain high speed while stuck at an intermediate altitude, the only way to meet your ever changing descent profile is by using speedbrake. Whilst prudent use of speedbrake is definitely one of the tools at our disposal, the net effect of being held up and using speedbrake is an increased fuel burn. As you may be aware, ek drivers are under considerable management pressure to minimise fuel burn, not to mention our own preference to have more fuel in tanks. So in a nutshell, slowing down when held up is first choice for any thinking operator of jet aircraft. If by slowing down it causes you difficulty in flow control, then you need to assigne speeds. It works in Heathrow, it should work here.
On the other hand if you expect us to guess what speed you want, you are going to get a variety of results.
V