Hi Gray,
I hope you will take my response in the manner in which it is intended.
Wild camping, though popular under a bushcraft heading, is illegal under trespass and criminal damage laws. As such, BushcraftUK cannot recommend anywhere to go, as that would be advocating illegal behaviour. Access to any land should be with the full permission of the landowner.
That said, there are plenty of people who do it and return to civilisation leaving no trace of their transgression, but we ask that they do not discuss it openly on the forum, nor openly recommend places to go. You might recieve a few answers by private message, but again I ask that you don't promote the activity on the forum.
I am led to believe that certain areas will allow you to "wild camp" within certain boundaries, and I ask that you stick to these places after independant research.
ATB
Ogri the trog