I asked the same question myself at Specsavers last week - I had some SS prescription sunglasses frames which I broke on holiday in Santorini and urgently had to replace the frames at an opticians out there at a cost of 80 euros. They are Italian designer ones which I really love but SS made it as difficult as they could for me to have new lenses put in these. They said they would do it but if they broke they would not attempt to mend them as they weren't supplied there (fair enough I suppose) but the cost was prohibitive, not worth doing so I didn't go ahead but chose some from SS range which I don't like half as much.