Things for (early 20s) couple to do in London?

We're going on Thursday for the weekend - on Friday night we're going to Fabric but otherwise have nothing much planned. Any recommendations? Have both done the bus-tour (separately), I've been on the Eye and wandered Southbank, but my boyfriend hasn't stayed in London since he was about 14. We're staying in Richmond but have Oyster cards and we're not afraid to use them! Also, does 'Sugs' pub' (sp.?) mean anything to anyone? The boy mentioned it in ping - a prize fighter or footballer or something (called Sugs, though that's not the name of the pub) is the owner...