The Sci-Fi-London Festival is holding an Irwin Allen all-night event on Thursday 28th April 2011 at the Apollo Piccadilly Circus.  The screenings start at 11.45pm.  Tickets are free and must be reserved in advance.  Episodes being shown are:

Voyage to the Bottom of the Sea Pilot Eleven Days to Zero

Voyage to the Bottom of the Sea Original Unaired Colour Pilot

The Time Tunnel Original Unaired Pilot Rendezvous with Yesterday

The Time Tunnel 2002 Remake

Land of the Giants Pilot The Crash

Land of the Giants Original Unaired Pilot

Note that the Irwin Allen night is being held on the eve of the Royal Wedding so transport in London may be pretty busy on the Friday, so allow extra time for returning home.

Sci-Fi-London Festival Website