I was in Sainsburys today and saw they had the Piz Buin 1 day long sun tan lotion on offer of buy 1 get 1 free. (approx £12.99 each)
I then noticed that the factor 8 one had been reduced from approx £12.99 down to £2.99 and was still buy 1 get 1 free. The catch is, you get the cheapest one free.
I bought 2 of the factor 8 and only paid £2.99 for both of them. I then got some factor 2 x 15 and also factor 2 x 30 and paid £26(ish) for them.