Speaking as an ex-pat from Manchester (well the posh bit in Stockport) who's loved down sarfff for 20 odd years I'd see keep your guest inside the M25 if it's her first visit. Plenty to see here. 1) Charing Cross after 1am 2) Leicester Sq when the pubs and clubs let out 3) Any central London A&E at about 2am 4) A central or northern line tube when it's really hot and humid on a weekday rush hour 5) A kebab shop after the pubs let out in Wood Green Hey - it's all there ! London has it all.