Canteen (Spitalfields or Royal Festival Hall, 0845 686 1122) serves super-traditional food such as devilled kidneys on toast, kippers, mushy peas and orange jelly, for less than you'd expect, in their ultramodern booth-style restaurant. Very efficient and most mains cost under a tenner.
Otherwise, try The Reliance in Leeds (North Street, 0113 295 6060) – a more-gastro-but-still-pub restaurant which does the usual hearty bangers and mash and pie options, and even has a pub quiz on Sunday nights.