tubby,
Being told to slow down then finding out there is no delay or that you can maintain high speed then be told to hold is obviously an internal comms problem in ATC for which there is no excuse. Unfortunately this is not something new!
As for controller appreciation of pilot workload caused by last minute changes. It is still possible but more difficult than it used to be for NATS controllers to do familiarisation flights. These have always been voluntary. NATS managers did not help the situation by regarding them as 'jollies' and insisting controllers do them in their own time.