Just had an email from Millet Sports, and it seems there are lots of great discounts when combined with the extra 15% off, better yet the code works on Sale items too!
Code to enter at checkout: EXTRA15
Quite a variety of items in the sale as well. eg. Nike Inter Milan Stadium Jersey was £16.00 in the sale, now £13.60 with free delivery! Adidas Gym style Ladies pants were £21 in the sale, now £17.85!
Will put a few more examples in the first post.