Are BBC radio dramas based on books abridged?

I love fullcast audiobooks. I listened to a lot of graphic Audio. And I need more.
Very popular are the BBC radiodramas.
But when I looked up his dark material. The golden compass is only around 3 hours long. Which is far too short for such book. Are those books abridged?
Are there any excemptions?
I prefer Fanatsy/SciFi books.