As you've probably gathered most of the reviews are for the 'DVD' version of Lindsay Anderson's incendiary 1968 'bucking-the-system' classic. And the BLU RAY is available in both the States and the UK. But which issue to buy?
Unfortunately the uber-desirable USA Criterion release is REGION-A LOCKED although it doesn't say so on Amazon. So it WILL NOT PLAY on most UK BLU RAY players unless they're chipped to play 'all' regions (which the vast majority aren't). Don’t confuse BLU RAY players that have multi-region capability on the 'DVD' front – that won’t help.
Luckily the "Masters Of Cinema" release on this side of the pond (which boasts the same cleaned up transfer) is REGION FREE – so that will play on UK machines.
Check you’re purchasing the right version before you buy the pricey Criterion release...