Very quick comparison list (may contain errors as it was very quick)
All based on 100mg 64 tablets i.e. cheapest deal
(there are other considerations i.e. if you want half or a quarter of that dose)
Superdrug £100 for 28 tablets max amount offered so £3.57 each
Boots £56 for 16 tablets amount offered so £3.50 each
Asda £90 28 tablets max amount offered £3.21 each
Lloyds £48 for 16 tablets max amount offered £3 each (£2.50 with subscription)
pharmica.co.uk 64 x 100mg £139.99 sp £2.19 each
(Their comparison chart says Lloyds £304, Pharmacy4U £272 etc)
DrFox £49 for 32 tablets max amount offered so £98 for 64. £1.53 each
Postmymeds £84.00 or 80.74 after discount so £1.33 or £1.26 each
chemist-4-u.com 64 x 100mg £74.99 so £1.17 each
Menschem £74,99 or £63,74 after discount so £1.17 or £1 each
Thefamilychemist £71.99 64 x 100mg so £1.12 each or 96p after discount
Just now knuckles' suggestion clearly the cheapest 300%