This would presumably allow the Horniman to make a great deal more money out of the events they put on (e.g. fairs & wedding receptions). Considering how vital this museum is to the area as a cultural hub, I think that this is surely worth a little local inconvenience when an event is on.
My understanding is that their finances have been hit hard by the economic situation. Any ideas they have to increase their income without required extra expense from the visitors should be applauded.