I never mentioned why I started the thread in the first place.
When I head towards Kielder it is usually up the road through the village to Scotland. But my memory of the actual forest was a good decade plus ago, riding through maybe a place called Falstone to exit northwards. The forest had a bit of a centre parcs feel to it, family groups and juniors doing exploring.
It is slightly worrying that juniors would not have such safe freedom to explore, parents needing to be more watchful.