I haver the BG one, and yes for £15 its expensive. But I find it amazing truly, the amount of sparks that fall and the heat. In one strike you can get 10 times more sparks than witha standard magnessium fire steel, which I also have.
I have tried lots of veriations and have found it to be the best, it also has a waterproof section for cotton wool.
Its brill,
Bear