Enquired about the Horniman when looking at wedding venues last year. Bloody absurdly expensive and the catering was limited. But lovely conservatory.

Non-local tip - many of the restaurants in the City charge no fee for venue hire (so not £5k-15k down before got food/drinks/music), instead they have a reasonable minimum spend. Ended up choosing between the Samuel Pepys and Chiswell St Dining Rooms. They were by far the best value for money unless willing to do own catering.