Don't forget to try out the echo in the British Museum Round Reading Room in the new Great Court: yodelling works best.
You'll find single person urinals on many street corners, some are red and some have glass sides. Dial 999 to flush.
London cabbies hate to be tipped and love you to haggle over the fare.
Want a free meal? The Queen runs regular Garden Parties at Buck House, just go along and join in.
Bringing your hunting rifle? Try potting the pigeons in Trafalgar Square.

RtS
(Don't thank me, just enjoy....)