The reason they are called 'bags for life' is that you are supposed to take them back to the supermarket when they split, they should give you a replacement one and recycle the old one into more bags. That's what I understood, anyway.
We went to Sainsbury's today too and were given packs of Lego collector cards - presumably we are now meant to buy a book to stick them in and keep spending to get more cards and fill the book.
I can’t believe you would take.it back for 10p ! If you feel strongly about it turn it inside out or use it as a bin bag but taking it back for 10p I find laughable