As far as I am aware all land in the UK is owned by someone, so theoretically every cache needs land owners permission. If the reviewers insisted on this then it would kill geocaching.com as clearly almost no caches would get placed. Certainly roadsigns, crash barriers, town centre seats are all owned but permission is never requested.
As far as hedgerow caches are concerned, it’s not so much the placement of the caches that concerns me, but the actual caches themselves. But that raises the question once again of what is the difference between a geocache and litter. Many of the hedgerow caches really are only litter and it will be interesting to see the first prosecution of a cache owner by a local council. After all, they have prosecuted for cigarette ends etc, and we leave our contact details on our litter!
The worse cache of this type I have come across is one in Cornwall which was placed inside a TV set which had been fly-tipped over a hedge! What sort of example does this set and I can’t believe some of the logs which praised the placement.