Hi Maren,
The dacts are on marshy land called Willow Carr, just outside the North West corner of the Security Fence which surrounds NSA Menwith Hill, near Harrogate, North Yorkshire. Menwith is the largest American base in Europe, It operates outside of UK, EU and (according to Edward Snowden) US law. Be prepared to have your number plate recorded should you visit by car! (Whilst photographing the white form I was shadowed by a police motorcyclist on the other side of the fence.)
Tim DH