Just came across the reciept for a great lunch we had in a SOuthern Indian Restaurant in Croydon which is still considered London and is easily reachable by train (maybe even tube?)
The place is CHOLA DURBAR 62 South End, Croydon
PHONE 0208 688 6996
the restaurant was fairly new and empty but we had a delicious interesting and fresh lunch. we had a few dishes including a great selection of pickles and chutney which were unique to what we ever had before. Unfortunately I cann't remember all the dishes but the impression was that the food was more authentic that typical curry houses. We had some sort of dry cooked lamb with pieces of roasted coconut, Also a mango yogurt dish - not at all like raita. They really specialize in Southern Indian (yes we did have masala dosi and the chutney was v. good)
Anyway, in general Indian in England is much better than here in the US, but this was really different, reasonably priced and delicious. Check it out if you happen to be in the area or live in London.