DC have never been to the NHM, I've avoided it so far because of how busy it is these days in the school holidays (did the Science Museum one half term, never again)
Their school has an inset day the Friday before October half term, which will be a school day for most SE schools as far as I can see.
Has anyone been on a term time Friday and can tell me if it's still horrendously busy? We'd stay at my mum's in London the night before so should be able to get there for opening time.