It's heavily market-dependent. Assuming you're in the UK you might be able to find something. I've never had the chance to use any of them myself but there were definitely some valid discount codes in the past; this post lists a whole lot: http://loyaltylobby.com/2012/11/16/e...otional-codes/

The discount was typically 5 to 10%, with 15% being the most I've seen.