There's a great little magic stall in Covent Garden called Magic Cave. Holborn station is just minutes away from there, which is minutes away from International Magic shop! Go there if you can. Fantastic place.
My personal favourites are John Bannon's Last Man Standing (Impromptu and only a little bit knacky) from his book Dear Mr. Fantasy and The Bannon Triumph/ Play It Straight is virtually self working.
Just a suggestion for those who are unable to redownload the trick Ollie, you could upload the handlings to YouTube and make it an unlisted video, sending the link to those who wish to watch it (me, me, me, me, me).
DK
David Stone's trick William is a very nice, completely impromptu way to reverse a card in a pack. It's on one of his Secrets of David Stone DVD I believe.
Wormhole from David Acer's book More Power To You is one of the best types of these tricks I've ever seen.
It's also redunkulously simple and, oh yeah, funny too.
D