I did this yesterday after finding it on MSE.
First I topped up my mobile phone twice with £5 to get two £5 No7 vouchers and £3 haircare vouchers
Then buy any 6 items from the No7 suncare range - not self tan - and you will only pay for one! Then get another £5 off with one of the vouchers. The suncare range includes pre holiday moisturisers etc. 6 lots cost me £3.50 yesterday with a saving of £39!!!!
This works because suncare is bogof and No7 is 3 for 2 and both offers are working.
Be quick though as someone on MSE said yesterday that Boots might be on to it.