I finally have the gift of sight! I took the glasses back to the optician yesterday and she did some adjustments to the nose rests and the arms, and flattened the frame so that it's less curved, and I can now see! I'm so happy!
I was told when I was younger that I couldn't have contacts, so I've never bothered. They never told me why, so it's probably a load of rubbish! I actually look better with my glasses on that I do without though, so I quite like wearing them