Available online and in-store (presumably, I've not been to a store to check) if you spend a minimum of £15 on any Star Wars Lego product.
The deal runs from 6th February and ends 4th March 2012, subject to availability.
Their website suggests you can buy the set on it's own, for £4.99
, which seems a little steep! Could be a good way to get more than one if you so wish, otherwise, you'll need to split your purchasing into separate transactions over £15.
to see the sets they have available online.