London Road in Forest Hill is closed for a couple of weeks for emergency sewer works, see http://www.bbc.co.uk/news/uk-england-london-10979932. This will result in additional traffic on Dartmouth Road and Sydenham Hill and these roads are probably worth avoiding if you can.
But the good news is that it makes the Horniman and Forest Hill town centre peaceful and pleasant to visit by foot or by train (every 4 minutes from Sydenham). A guide to what's on at the Horniman can be found at http://www.horniman.ac.uk/events/eventsnew.php
South Circular Road Closure
Re: South Circular Road Closure
and there will be an impromptue picnic in the road, between thai cafe, and italian deli, this Sunday (weather permitting)