Fancy some dress-down Friday action all in a good cause? All you need to do to take part in Jeans For Genes day tomorrow is (unsurprisingly) wear your fave pair of denim trews, then dip into the pockets to donate some cash to an amazing, lifesaving charity. Sounds good, right? Right. If you're looking to update your denim style, then check out these two easy-as styling tips from this week's catwalks, and work your jeans (for genes) for SS15, tomorrow…