I have just read through this; 6 years or so of posts full of people frustrated with the system. The solution we are building is kind of a combination of living on the land, and van living. Look at the nomadic living forum on ukhippy for loads of info on van life:
http://www.ukhippy.com/stuff/forumdisplay.php/50-Nomadic-Living
Forestry land has more generous permitted development than agricultural, (plus it has lots of trees to hide your illicit activities!), so a storage shed or two shouldn't be a problem, and you can have a caravan which can be used for seasonal forestry workers for an unspecified length of time. You can then grow your food, keep chickens etc, and partially live in the caravan, partially in your van. Have in mind some local places to park your van, and if anyone starts sniffing around causing hassle, sleep in the parkups for a few nights/weeks, or stay with friends/family if possible
There are quite a few people living in vans, trucks etc full-time, so planned well, this system is perfectly do-able, and in the meantime, you can plant thousands of evergreen trees, shrubs and vines to form a total barrier between your land and any public access. You could also look at putting in a well-hidden small dwelling, buried in a hillside maybe, and surrounded by evergreen trees or thickets of blackthorn. Look at tiny homes for ideas, perhaps survival bunkers etc, and adapt the design to your surroundings.
Forget it if you have kids, but if you are a quiet and discreet individual or couple, build good relationships with your neighbours if you have any, and don't draw too much attention to yourself, I believe that a semi-nomadic lifestyle like this could provide you with a really lovely, free way of life, without having to jump through all the hoops and pay thousands to support a system that does nothing to support sustainable, low-impact living.
I can't even stand the thought of applying for planning permission. I do not believe that I should have to, so I refuse to play the game by their rules.
Nobody can tell you you can't spend all day, every day on your land, all they care about is where you sleep at night. We just need to re-think our lifestyle to adapt to this mentality.
By viewing living as a modular system, rather than a static home inside a single box, we can be free of these constraints!