I was under the impression that they will be doing a "move", which will include moving over props and theming from Tooley Street to the County Hall? Through the opening times page on their website, they have confirmed opening times up to 1st January 2013, with no break for the move.
I believe they will wait for the dust to settle after the holiday period, before conducting the move between mid-January and mid-March. They'll make sure the new Dungeons are open for the Easter Holidays
I don't think they're "moving" it all. The props/sets are all dated, I am sure they'd rather get a whole new lot in! They'll probably move the ticketing equipment and such, but that can be done in an evening.
This is just really interesting as it's the first time (in a long time) that an indoor attraction has re-located.
Unless it's changed they were closing an unspecified date in December until the reopening at County Hall.
Whichever, they are underway with it all as we speak.
Exciting! Have you wandered past County Hall and seen this happening?