blatant copy from mse
"The Advantage Card Machine may give you (cos we know we don't get all the same things) a coupon for 500 points when you buy 2 Olay items or you can use the current vouchers as well. So if you get 2 of the Olay Total Effects Cleanser that are £5.86 each, this is what you do:
Go to a manned till (it doesn't work on Self Service), present your 2 Olay Total Effects Cleanser then 2 x £5 off vouchers, followed by your 500 points voucher.
You may meet with surprise/amazement/shock/refusal from the SA - I've had them all!
But the bottom line is, you'll earn £5 in points, plus 2 bottles of whatsit, and it'll cost you 2 x 86p = £1.72!!!
Now that's a result. I was kindly granted 5 vouchers in total, so did it 5 times, so £25 in points, 10 bottles of stuff, worth £58.60 all for £8.60! A very nice profit of (drum roll)
And you'll get another £5 voucher each time!!!!!!!
There are several Olay items that you can do this with, but the cheapest is:-
Olay Total Effects Cleanser, radiance enhancing cream wash
7-in-1 anti-ageing, with exfoliating micro-beads"http://forums.moneysavingexpert.com/showthread.html?t=1848727