Actually, you've just reminded me of two places:

1) The "Super Sandwich", a Russian-run sandwich bar near "Silicon Roundabout" in London, now sadly gone due to being situated in a building earmarked for development that mysteriously caught fire one night. They did wonderful, tiny, peppery beefburgers (rare, if you asked!) with a mix of cheese and spices in a (not flattened, lightly toasted) panini. An old favourite.

2) A late night sandwicherie in Strasbourg (I think it's now just a Pomme de Pain). Used to do (always rare) steack haché frites, all in a baguette. Ultimate junk food