Nigelondraft
I understand your point about being told to fly a high speed, only to be told a few minutes later to hold... unfortunately thats often the only way we can maintain an order and also get aircraft safely into the hold.
If we let aircraft wallow down at a poor descent rate then there's going to be alot of avoiding action handed out as a blob of aircraft arrive at holds at levels which are not seperated from adjacent holding areas, nor from other aircaft wanting to enter the same hold!
It's not a probelm unique to the LTMA, but it is exacerbated by the large number of busy airports crammed into a relatively small area.