I haven't been to the Dewaniam for a couple of years, but it was very nice.
And if you are prepared to go all the way to Penge, then you might also want to try out Ganapati in Peckham.

But if you are looking for somewhere nice right in the centre of Forest Hill you should probably consider Tse's and Dartmouth Arms. But with a two minute train connection to Honor Oak Park, I continue to believe that Sodo and Donde (Tapastry) are virtually in the centre of Forest Hill.