Edit: The Amazon page you’re directed to is saying £7.19 though if you look to the right you’ll see just below where it says Other Sellers on Amazon that it’s also saying £5.99 Sold by: Caulfield Industrial. Click on the Add to Basket button.
I just bought a clear pair of these for £6.49 via third party seller blueacetradingltd2 to avoid p&p, I'm mainly riding when dark at the moment while heading to work as I’m currently working night shifts. Not bad as they’re only 50p more than the smoke pair. Also £6.49 via Prime Caulfield Industrial.
According to camelcamelcamel it’s also possible to pick up a pair of the ESP's for as little as £4.60(ish) via third party seller and as little as £4.80 for the smoke lenses if you fancy watching these.
Smoke lenses are currently selling for £5.99 plus free delivery via Prime though currently £7.99 via third party seller blueacetradingltd2, and pair with ESP lenses (tinted) can be picked up for £6.85 via Prime Caulfield Industrial, £6.99 plus free delivery via blueacetradingltd2.