There'll be someone else along to say this, but I may as well: I don't think it's worth spending much on sunglasses, just get something that looks good enough and has UV protection or whatever you're after, then it's no big disaster if you sit on them (like I did with my last good pair!) and they break. Just bought myself some new ones from boots with a half price voucher. Do the job, look good, and most people can't tell the difference between these and expensive ones, nor do I care if they can.
To help with real answers, any particular style that you like? I find that some shapes suit my face and others dont, which can make a big difference when it comes to them looking good.