Sorry for putting this here, but you're such a clever lot 
I bought John Frieda's 3 day hair straightening spray and protector ysterday from a large supermarket. It was £7. I tore one of the flaps off the box when I opened it. I used it this morning, following the instructions to the last letter, and I may have well have sprayed prit-stik glue into my barnet. Had to wash it off straight away. I have box, albeit ripped, and receipt.
Am I within my rights to take it back. £7 is £7!