Hard to find this kit in stock, let alone with a discount. Zavvi have it cheaper, but they have had it marked out of stock for weeks now. It's a massive kit to build. helped a friend build theirs but still looking to buy my own. It is about the same size as the Liebherr 996 excavator.
Link to Lego information page: here
Edit:
For today's extra content, I remember we had one of these in at work a few years ago. The real one, not the Lego kit… The Lego kit may or may not be the same scale :P
I managed to get the Top Gear 2nd hand for $30. But retail it's well > $100 for ~450 pieces.
This one has almost 4k pieces, but gosh, a lot of the price of this and the Top Gear car is for the Control+ hub and motors.