Try Indian Summer - not sure where it is, but they will deliver - their food is superb, always high quality, great choice and they give you a customer number when you first order, so you don't have to give your details everytime you call them - just the number.
Restaurant/take away I've known for for 7 years (...gosh). Always under same management. They do cheerful, efficient local delivery and have rarely disappointed.
Mr Miah really does seem to care about food quality over price, just don't get into any discussion about good sources of fresh coriander or tiger prawns.. you'll be there all night.
They have a takeaway annexe, Tandoori Night, 6 Trinity St 020 7357 7010 which does pretty much the same menu (and actually cooked on the premises) which is also good, but they work on a cash only basis.
Had plenty of curries in SE1 and can't reccommend them highly enough
Simply Indian on Tabard Street was also delicious, IMHO. While they're mostly based on take out/delivery trade, also have a few tables on the premises. And you can bring your drinks - or even jugs of ale - over from the Royal Oak :o)