Thankyou for your replies.
We are both in our 30's (no kids yet), and not really the sort of people that like to party all night, so we ruled out Soho House quite early on. We are more interested in old-style luxury than minimalism too, so that ruled out the Mandarin Oriental and the Gaansvoort.
We're going from the 18th to 22nd September, and have been looking at the Suite Life promo for the Peninsula.