>>608563There's quite a few areas where you could live off the land even without owning it. Parts of the lake district, northumberland, scottish highlands, etc
Even sussex, which is highly populated, has some big forests full of deer and rabbit and game to hunt and plants to forage. I've camped there and never seen people deep into the forests.
The UK may have lots of people but there is some wilderness. There was even a guy who built a house next to the beach and lived there for 20 years before anyone saw him. There are probably a few people living off the land in the UK right now.