Oh and as regards to going to Central London...
There's a few options...
1. Getting the 286 bus that takes you to Greenwich (Cutty Sark) and then getting the tube from there to wherever.
2. Getting the 286 to Eltham Train Station and then getting a train to either London Bridge tube station or Charing Cross, then getting the tube from either of them stations to wherever you go.
3. There is a night bus (N21) that stops literally a 5 minute walk from the Avery Hill Residences, you can get this from Charing Cross.
I've been to Central London a few times without a problem (as far as I can remember lol).