Are you honestly comparing a 3 terminal airport in MAN which handles around 22 million to a 3 terminal airport in SIN which handles 54 million passengers.
Not at all, they are different airports serving different markets and the fact they process more passengers is irrelevant as they were designed and built much more recently than most UK airports to do just that.
The point is that whenever anyone has a moan about their latest UK airport experience they tend to quote airports like HKG and SIN as being the holy grail, when in fact they all suffer from congestion and queuing same as any other airport when there's a peak in demand.