Although am mainly a tea drinker [after dinner coffee an exception] Mr L complains that if he orders a latte or cappuccino when out and about mid morning, he never knows what size cup will be given.We go to mainly independent places, and they vary wildly, a 'small' in one place is medium in others, and large could mean a fairly normal cup through to a mug size or a small bucket!
To think that London, or anywhere else for that matter, does not belong to any one demographic