Ok, you need a bit of confidence for this one as you are taking advantage of the B&Q price promise and the 15% Homebase sale that is currently on. This applies to any product really but I have chosen the Miracle Grow Compost as I bought 8 bags today for £30.60.
Basically B&Q and Homebase sell the bags for £5.99 each and 2 for £10, however homebase has a 15% off everything sale Today and Tomorrow (Fri/Sat) which I posted earlier in the week. That makes the 2 for £10 offer, 2 for £8.50. However if you go into B&Q, stock your trolley, go to the check out and mention you would like to take advantage of the price promise, they will get their manager, maybe call homebase to confirm (but they know of the 15% sale) and ring through a discount to make them £7.65 for 2 which is an extra 10% off the £8.50 Homebase are doing it for. My B&Q has a massive banner outside the store about the price promise - it's there - take advantage of it.
You have until Saturday night.