Try SpecSavers. They had the contract last time I looked. Service was cr^p so they may have lost it.
I used to go to Kelvin House - had the test - got the prescription - got the glasses from Med Centre. Easy peasey.
Then had to go to Spec Savers - had the test - got the prescription - got the call to go back - had them fitted. Man said have a look through them.
Could not see the end of the shop