I had a poor experience with a major high street optician a few years ago. Two pairs of spectacles and the free sunglasses were all made up to the wrong prescription. Now of course the problem here is that for many people, a change in prescription takes a while to get used to, so it is normal to persevere for a couple of weeks, until you finally realise that something is badly wrong. A pharmacist would not survive if he/she supplied me with 3 lots of tablets which did not match a doctor's prescription so why is it ok for a chain of opticians to just shrug their shoulders when confronted with evidence from another optician?
I have now found a stand-alone family run optician who make up spectacles on the premises. The person who makes my spectacles is as familiar to me as the optician who carries out the eye test. I am convinced that there is no other way.