Evolution Fusion RX4 Prescription Shooting Glasses From MPR Sports 

These were supplied by MPR Sports on Ebay, £35.95, link at the bottom.
Matte Black frame - Interchangeable 4 Lens Set supplied with Grey, Purple, Orange & Yellow lenses plus prescription optical insert - Quick and easy lens changing - Impact resistant, shatterproof polycarbonate lenses (comply with EN166F) - 100% UV protection
Supplied with detachable prescription optical insert - all you need do is take the optical insert to your usual opticians and ask them to put lenses in to your normal prescription (we also provide this service).
Flip-up lens design if you want to temporarily look through your clear prescription lenses.
Supplied with soft carry pouch, cleaning cloth and a hard case.
It cost me £70 at Vision Express to get the insert glazed. These glasses are going to perform very well!
Find them here: www.ebay.co.uk...