Get a free annual pass for Legoland when you spend £50 in their shop.
I have done this for a few years now and got free passes for all the family. I spend the money in their shop and then sell the lego on Ebay, therefore getting an almost free pass!!!
The £50 offer expires tommorrow (worth going for the fireworks)but there will be a £75 offer at Christmas when the park isn't open but the shop is (so no entrance fee). Details of this one are on their website.