Mela is pretty central and good, and the staff are friendly and knowledgeable: http://www.melarestaurant.co.uk/
If you want something a bit more authentic, though, I can’t do better than recommending Tayyab’s: http://www.guardian.co.uk/lifeandstyle/2005/may/07/foodanddrink.shopping1. It’s small and crowded, but the food is out of this world. Well worth the wait, and there often is a wait, with the queue going out of the door and into the street. If you can have your meal at a slightly off-peak time, it would help avoid a long wait.