And having flown them a few times i think not about 1.5 over the city is decidely iffy for alighting clear(except maybe taking the Mersey) and marginal legally and as such I'm always gunning for not above 2 if poss.
I asked one of the controllers there once why it was such a low limit, and he said it was a historical thing dating back to when the airspace above was Class A and it was to therefore avoid having all the GA SVFR...if that airspace IS now class D is there any possibility of the standard zone clearances being not above 2??