I was trying to compare apples to apples, but I don't think you noticed. Manhattan is not the equivalent of N1 - mainly because Manhattan is a very odd apple. (land constrained district of a much larger city). Also, the UK only has 1 international city (which I chose to define arbitrarily as whatever backs my arguement up), the US has several. Manhattan to my mind is possibly equivalent to WC{1,2}, W{1,2,7,8,11}, SW{1,3} together - but even then I wouldn't consider it to be an exact thing.