It has public rights of way (if on foot, horse or bicycle) crossing the whole country. You can walk from one end of Britain to the other without trespassing, and without using roads (much). Many of these paths are very, very old, in a few cases Roman or pre-Roman, although more are medieval. Until recently, they were based on common law rights, although they're now in statute. The situation is a happy hangover of the medieval approach to property rights, which is based on custom and usage and negotiation instead of strict statute. The American eighteenth-century enlightenment approach is an attempt to make everything tidy: it's based on the rationalist idea that a thing is its definition and nothing more. So private property is private, that means nobody else can use it: case closed.
The medievals also held in theory (not always in practice, hahaha) that one had a moral duty to use wealth for the public benefit, and that not doing so was theft. So buying up land and kicking everybody off was not only frowned upon, but could also get you into legal trouble, and possibly into trouble with the Church.
EDIT:
A few points since I didn't mean this to be a controversial comment but it seems to have started an argument:
- I should have mentioned the vast public lands in the western US, since they provide a counterpoint.
- The liability issue in the US obviously affects access to land, but could be ameliorated in principle (I would think).
- My comment is not a general defense of British land usage approach. There are huge problems, including but not limited to the tiny number of big landowners. I should have prefaced my first paragraph with "in some respects". Similarly, it is not a general defense of the medieval approach, and certainly not of serfdom.
- The UK's problem with vast landowners got worse in the sixteenth, seventeenth and eighteen centuries, with the Dissolution, the enclosure acts and clearances. Land becomes far more concentrated at this time, and the social distance between landlord and tenant much greater. Older lords' houses tend to be built very near roads where anyone can talk to them (whether to beg or to threaten), whereas the eighteenth century ones, as well as being much bigger, are far from the road in huge parks, guarded by layers of servants. The historian E.P. Thompson talks about the "triumph of law over custom" -- in other words, "what you and your ancestors have agreed with us and our ancestors up until this time doesn't matter, we've managed to get this law written down that gets you off the land, now get lost".