Tiroler Hut is a bit of one-off and may just be what you're looking for if you absolutely have to pull off a rowdy night out.
More restaurant than bar, it fits better in the 'Hidden Gems' section of the site (so you need to book). Unusually for London it offers an Austrian dining experience (no, me neither), complete with authentic food including bratwurst, wienerschitzel, jägerschnitzel and sauerkraut. All washed back with out-size steins of lager.
The staff at the Tiroler Hut dress traditionally and expect knee-slapping, raucous singing, lederhosen, cow bells and an accordian to feature at some point during the evening. Not the place for shrinking violets to pass a quiet evening, but lots of fun and memorable to boot.