From Trafalgar Square, China Town is only a 2-3 minute walk. We went this way actually for lunch. The place is strewn with all you can eat Chinese buffets for cheap. I also a couple of theaters around the area.
The buffets are mostly located on the ground level area with some having seating on the second floor as well. Our lunch was either 4.95 or 6.90 pounds. I can’t remember since I didn’t pay. ^^ It was really affordable and the food wasn’t that bad. It wasn’t great either but it’s cheap and you get a lot of bang for your buck.
I wish I had taken pictures of the food but I was so hungry at the time.