Tay Do Cafe, at the Southern end of Kingsland Road, is often cited by visitors as one of the more reasonable value venues on offer, and is a regular feature in Time Out's "Cheap Eats". Whilst the decor is very canteen-like, it's BYO, and the food is pretty good. It's one of those occasions when "eat out for under £10" is actually true.
For more information, see the restaurant's page on the Time Out website at http://www.timeout.com/london/restaurants/reviews/13848.html.
Click here to see the location on a map.