I dunno about 'up north' but down in Surrey and Middlesex the boundaries tend to vary whether you are talking about council borders, parish borders or 'postal sorting office' districts..
This is further confused by a large borough taking the name of a town within it..
the worst is the 'laziness' of people calling a HUGE borough like
'London Borough of Richmond Upon Thames' *just* 'Richmond' when referring to a small town within it..
(LBRUT is more than 22 sq miles in area, and about 40 miles end to end!)
More confusion when people turn up to Richmond station, and are then told they meant Ham, a small town near Kingston!!
And of course there some companies say they are in 'London' for snob value..