Dan Radcliffe, Rupert Grint and Emma Watson are due to be guests all day long on the UK’s BBC Radio 1 Wednesday, July 15th.  According to our source:

This special “Harry Potter” day long appearance which will be broadcast from the set of Harry Potter and the Deathly Hallows. Readers Neil and PinkMoosley both report that popular host Edith Bowman and others have announced the Harry Potter day on the radio channel, where Edith will be on set of the final Harry Potter film. Also there is apparently a contest to be held for fans to win a visit to the set, however there are no further details of this yet online; updates to follow when we can!

Thanks TLC!