Just saw this on Money saving expert sorry if it's an old one.
Offer here, just choose shade and add to basket the code BRIDE should appear under your order at the side if not just type it in.
You do need to register on the site but YOU DON't need to buy anything else just pay £2.50 P&P and you should get your £12 mascara pretty much for free!!!
I have just done it and it seems to have gone through fine so good luck