Fairfield Halls & Ashcroft Theatre
The auditorium of this "Arts and Entertainment Centre" has possibly the best acoustics in London. Home to a good classical orchestra, it is ideally suited to showing films, concerts, comedy shows, theatre, and school speech days (yes, I speak from experience).
It's not very pretty from the outside, although the changing coloured lighting attempts to liven it up at night, but the venue is good nonetheless and provides a wide variety of entertainment to a wide range of audiences.
See www.fairfield.co.uk to find out what's on.