It's probably a fake.
I detest his political views, but I'll be surprised if it's genuine.
I mean, the signature is blanked out, but the writers name is shown at the top.
Letter headings in those days had a structure that is missing from that example, the post codes just don't make any sense either, and it's all a bit convenient with elections just around the corner.
If someone was writing a letter on a matter that was of concern in those days, especially one that went on for 3 pages, it would have been typed in a more formal manner, and letters were never numbered at the top of the page, if they were numbered at all.
In 1981, parading around singing Nazi songs would not have provoked any sort of disgusted reaction, and was the term extremist used in those days?
If it's genuine, I'll hold my hands up and admit my cynicism is misplaced, but looking and reading it just doesn't sit with my recollections of life in 1981.
I'm no supporter of UKIP, as I've stated, but shit like this annoys me more than the verbal diarrhoea politicians come out with on a daily basis.