According to this website, it appears to be the 2000 reissue of the kit. (Surely Airfix could have waited a year and reissued a 2001: A Space Odyssey kit in 2001, but noooooo...). I don't have any personal experience with the kit, but here's a brief online review.
I have the original Airfix model that I had built a loooong time ago (70's). Airfix wasn't known for their accuracy, but I thought that the Orion was a fairly good representation of what was on screen. I'm planning on re-doing the whole thing (removing parts, re-gluing and painting it).
I have a really detailed paper model of this I got from UHU-02's archive. it is really beautiful. It even has a highly detailed interior... I just have to print it out and assemble it.
It is something else, for sure!
Not very big. UHU02 specializes in amazing miniatures. I would guess it's about 12 inches in length. I have only seen the pictures, I haven't built it yet. But if you like high-quality paper models, this is his site: http://uhu02.way-nifty.com/ He is in the process of making an ESB AT-ST right now. You can also follow his work at zealot.com
I built the Airfix one many years back. As others have said it's not the most accurate, but it builds to be a decent piece and if you get it cheap all the better. Anything over $20 then go get the Moebius one.