I have heard of tours but not sure how you go about getting on one. I think some of the various clubs and societies do them occasionally - such as the British Association (which isn't the same as the British club.......ie doesn't cost the earth to join
)
Try googling for black and white house tours and see what you can come up with there. Singapore Walks might even do one these days - they have expanded quite a bit from their early days - or you could ring them and ask them - as they're in the tourism business they might be able to point you in the right direction if they don't do them themselves.
