How's this, then?
ANO, Art 255 -"‘Congested area’ in relation to a city, town or settlement, means any area which is substantially used for residential, industrial, commercial or recreational purposes."
Of course, it doesn't say you can't fly over a CITY!
And you couldn't fly over a settlement's microlight airfield since microlights - with one small training and one small hire exception - can only be used for recreational activities!
So a microlight airfield is "an area substantially used for recreational purposes" ie. a congested area!
Fortunately, it is all changed now!
(and as for the in-between times, where you could fly over a congested area only on take off and landing at a licensed airfield - did that mean you could t/o and land outside the hours it was licensed, or only within licensed hours?
Got to love the quality of lawyers and draughtspeople who work for the CAA and the government ;-)