As a native of Haltwhistle, I can confirm that everything Suibhne says about the town is absolutely correct. I'd be interested to know what the Significant Folk Associations might be, however.
As for Haltwhistle's claim to be the Centre of Britain, well, I was not consulted in this. But if you believe the astonishing set of statistics amassed in support of this claim and published on a sign in Haltwhistle Market Place, you'll probably also believe that the exact dimensions of the heavenly bodies are encoded in The Book Of Revelations.
In fact, the EXACT centre of Britain is a miscroscopic black hole located three quarters of a mile SSW of Haltwhistle Market Place, which often sucks in backpackers and passing woodland creatures. I myself have been sucked in several times. (The trick of getting out again is something one inevitably learns as part of a Haltwhistle Boyhood.)
Another of the town's claims on posterity: my great uncle Arthur Thompson was, in his later years, known as the Fattest Man in the North of England. Were he alive today, he's be one of the few people visible on Google Earth.
I could go on...
By the by, I now live in Sheffield, so I'm obviously attracted to the centres of things.