Specsavers broke my glasses and offered me a replacement at half price.

CardinalWolsey

Was the frame that snapped one that they no longer stock / sell? If they do still sell it, push for a replacement frame that they glaze with your current lenses. On the basis that 50% off at Specsavers equates to normal selling price (jn reality), and the markup on frames is immense, they could have replaced the frames and perhaps charged you £10 to do so and still not be at a loss.