The Beeb adapted the first two books of the original trilogy a couple of decades back. The cast included the likes of Christopher Lee, Spike Milligan and Stephen Fry, which tells you something about its tone. The production designer was Christopher Hobbs and understanding that he was designing for television - which at the time meant relatively small and low-contrast cathode ray tubes, decided to use more light and instead of following the gothic style one would expect, came up with a more 'Tibetan' style with references to the artists Max Ernst and Paul Klee.
A new adaptation was in the works, written by Neil Gaiman. You can guess what's happened to that.