Marvo -
By the way - the director did not ASK you to reduce speed, it was an instruction. Speed control is just that - control. It is not called "speed advice".
Also - yes on radar, a lot of units have a lot of information displayed on the screen, but to be honest I don't need a read out of the speed to know whether the pilot has managed to press the right buttons and slowed down - I (and every other approach controller!) can tell whether aircraft have slowed or not by the distance betweens the radar returns.
The flip side of this is crews who don't tell the controller that they plan to slow right down on final approach, slower than instructed, thus reducing separation behind them. By this time they are usually on the tower frequency. I will send around the aircraft who is unable to fly the assigned speed and can't be bothered to tell the controller rather than punish the chap behind who has done exactly as instructed.
Controllers can work around anything the pilots are unable/unwilling - but only if we are kept in the loop, in sufficient time.
louby