Buy Your Spectacles/Glasses Online for Cheaper

Under Opticians Act 1989, the optometrist is required by law to give you a copy of the prescription after the eye test, and you don't need to get the spectacles at the same shop.
http://www.opsi.gov.uk/ACTS/acts1989/ukpga_19890044_en_5

A few online shops from where you can get cheaper spectacles (in order of preference):
NuGlasses (08458336373 accepts ACCOR vouchers)
GlassesDirect (08456882020 accepts ACCOR vouchers)
SpeckyFourEyes (08448202020 accepts ACCOR vouchers)
WebSpecsDirect (08450706930 does not mention vouchers)
GlassesOnSpec (08712003720 does not accept vouchers)