The Hitchhiker's Guide to the Galaxy, the BBC TV show, is now available on DVD, region 1. Two discs, including the Making Of documentary, deleted scenes and more. The Amazon listing says "Recording of the radio series," though I doubt it's the complete recording, but you can get that on CD from Amazon.co.uk. This comparison of the region 1 and region 2 editions doesn't even mention the radio show recording on the disc.