Hi Dana,

There are plenty of good routes around Forest Hill. With plenty of parks it is easy to avoid busy streets, and a bit more difficult to avoid hills.

I have a 3 mile circle route through Crystal Palace Park from home but my hubby goes much more varied and different distances. Inside Dulwich Park the inner circle is completely flat and just over a mile long (good if you are doing interval training)
Peckham Park has a 10k race that is only 2 laps and has one gentle hill.

Hubby has 10k run from home to Crystal Palace Park, through Sydenham wood (or down College Road) round Dulwich Park and back home. It is hilly but he loves it.

Local running clubs that I have heard of: Dulwich Runners, Dulwich Park Runners, Crystal Palace Fun Runners and Crystal Palace Triathletes
They use local roads and parks so good way to find out new routes is to join one of them.