Ok, so far I have entered:

On Capital Radio's website:
Win a 5* Break with lastminute.com
Win annual pass to Cineworld
Win a digital camera

On Heart FM:
Trip to Prague
Win a laptop

Evening Standard:
Spa break

Oasis Online:
Sign up to win £500

Tickets to see Giselle the ballet
Tickets to see Cirque de Soleil

(can't even remember where I entered those ones!)

Maybe I ought to start with something smaller....