For the first time in weeks we made it to Kurz & Lang today, my favourite sausage-restaurant in London. Here you can get a Krakauer, Frankfurter, beef sausage or a plain Bratwurst with Löwensenf or (gloriously artificial) Hela spicy ketchup. Instead of Becks, that is served everywhere in London nowadays, you can try a fresh Flesburger or a cool Tannenzäpfle beer as well.
If you live in London and you like German sausages and / or German beer I can wholeheartedly recommend Kurz & Lang.
P.S.: No I don't get any benefits from them for mentioning the place.