As an English Brit I'd love to claim him for our own but, to be honest, I think "Scottish literature" is the only appropriate description.
This is awful news. I've not been a big fan of his later SF works. But Feersum Endjinn and Espedair St are tremendous and who knows, maybe the later works will grown on me. I hope he lives to see his latest book on the shelves.
(Edit: Not that I'm claiming he's not a Titan)