Instructions:As title really. Just found this in my inbox after getting back to work. 10% off with no minimum order value (seems that it can be used in conjunction with their BOGOF offes too). Discount isn't applied to the postage costs - £2.50, or free for orders over £10 - but they offer same-day dispatch for orders placed before 1p.m.
Looks like this has been running since last Wednesday, and is valid until 11.59pm tomorrow (Tuesday) night.