Dunno about plagiarism, but I'm not surprised if it's not a totally originally idea -- most ideas aren't :-) See also The Stone Book Quartet by Alan Garner for a smaller-scale example: four short stories around Manchester / Alderley Edge, spanning a couple of hundred years, IIRC. I really loved it because of the rich use of dialect -- I felt like had to guess the meaning of 5% of the words from context!
I haven't read Ulverton, though it's been recommended to me. I read another of Adam Thorpe's, Pieces of Light, mainly because the cover had a really cool "cloud leopard" on it, and the protagonist was called Hugh :-) It features the same character in several different phases of life (and in different places), with quite different writing styles for each. (BTW, your Ulverton link points to the widescreen DVD of the recent Hulk movie -- was that some obscure joke, or just a cut'n'paste-o ?!?)
