Hi there. I've had quite a lot of experience wild camping in Britain over the years. I've actually written a book about it! In England it's technically a no no, but if you're discreet, remain hidden and out of the way, only stay for one night, and don't climb over fences/gates you'll be fine. I've been spotted a few times by farmers and they've never minded as I was always very respectful, i.e- didn't start fires, didn't leave rubbish and didn't make lots of noise. The one problem you might run into though is finding a suitable place. It sounds as though where you're heading will be pretty green, but still, it could be hard finding somewhere. Most of Britain's land is tied up in fences, every inch of land someone's precious property. I've spent so much time getting stressed when tired and desperate to camp searching onwards and onwards for a decent spot to pitch up. Checking on google maps would be an idea. And don't let that put you off, when you do find somewhere good it's well worth the effort. There's something quite special about camping out in the wild, you feel at one with nature, a little vulnerable perhaps, but it's definitely an enriching experience.
Hope that's of some use. Ps. Check out my book here, you may like to hear of my many tales wild-camping:
http://www.lunchmusic.co.uk/Buy the Book/
All the best!