If the "problem" is the ability to move the lables arround with the posibility of having the lables the wrong way round when aircraft are close then NATS has only to look at it's Scottish ACC system where lables can and are moved around. They can also have a look at Ireland and France and many other places in Europe where the ability to move lables has been in operation for years without incident.
Perhaps the problem is not the position of the label or it's movement but the ability to distinguish the leader line ( the line attaching the lable to the position symbol).
Regards,
DFC