Indie London is reporting that Thursday, September 24, 2009 WB will launch 1,000 balloons  for a contest to visit the Deathly Hallows set:

Each balloon released will have a card attached featuring a unique code that will entitle the holder to register online at www.warnerbros.co.uk/harrypotterballoon between October 1, 2009 and December 4, 2009 for entry into the grand prize draw.

The grand prize draw will take place on December 7, 2009 – being the date on which Harry Potter & The Half-Blood Prince is released on Blu-ray and DVD.  The first prize winner will embark on a tour of the Harry Potter & The Deathly Hallows film set before they head off to make-up and wardrobe.  They will then step on to a set for a unique and exciting filming experience, where they will be filmed in the role of one of the magical framed “moving” portrait characters that have adorned the walls of Hogwarts in all of the Harry Potter films.

Fifty runners-up will also each win a pack of Harry Potter™ lenticular cards.

Thanks TLC!

UPDATE:  Apparently the launch takes place at 1pm at the Millennium Bridge and Matthew and Evanna Lynch will be releasing the balloons.