I've tried two other Indian restaurant buffets in London before. Spices restaurant is definitely the best one that I've ever visited. I tried the chicken buffet: rice, bowl of delicious spinach flavory chicken, on the side there was fresh salad with excellent flavors. My friend had the vegetarian buffet, she liked it a lot as well. Vegetarian was with rice, bowl of cottage cheese (made by themselves) in a tomato sauce. The menue changes regularly.
The staff was extremely friendly and informative about the food and its ingredients. The place is cozy. The whole experience in this restaurant was very good and positive, would go back at any time.