If you are in Old St area “Look Mum No Hands” is worth a coffee and cake, Vueltas on too, they maybe screening it (they normally do)
+1 for Greenwich and don’t forget the Greenwich Market then take a picnic into the park with a bottle of sparkles and two glasses.
Could take a river trip from Greenwich back into town, but thats a few quid.
If you are in Regent St/Oxford St area there are some pretty funky buskers there these days, though get there after 6 to see them perform, last week there was a “Jimi Hendrix Experiance” 3 piece and a drummer who was acting like a robot (I kid you not)
If you are after a bit of Posh then Langans Hotel for coctails too (though as said the Oxo’s got a way better view)
Erm.. Condor Cycles or Tokyo Fixed.
Another +1 for Boris Bikes.
Whitechapel Gallery (though you have to pay for this one) is excellent and has a photography exhibit on at the mo’
Sadlers Wells is a fave haunt of mine if you are around in the eve, then eat at the Green Banana across the road (very good veggie/fusion food) then walk up to the Angel.