Stockpot, W1D 4JL
The Stockpot serves good, simple food at very low prices. The menu is photocopied daily with constant alterations, but you can always expect to see soups and classic starters like garlic mushrooms, pasta, omelettes, salads and simple meat and fish dishes for mains, and desserts including sponge with custard! In short, the menu could be unchanged from 1954 -- and for all I know it is, as the Stockpot is certainly a long-time institution in London.
The restaurant is basic and busy, with tables crammed together and a large basement for overflow. No bookings are taken. Food is served very quickly, and throughout the day, making this an ideal refuelling point between pubs.
For me, the Stockpot is the epitome of George Orwell's cheap, hearty 1930s Soho restaurant catering to the masses, with red checked table-cloths and a whole meal for three-and-sixpence (see "Keep the Aspidistra Flying"). It is probably the last of its kind.
A quick lunch should be �6, and a full meal with lager or wine will be under �10.
Another branch is in King's Road, apparently -- I have never visited.