I am a bit late on this, but Bad Dice have a 2 hour podcast with ex-Games Workshop employee Gav Thorpe. Gav is best known for being the Warhammer Loremaster (?). He was with the company for 15 years and in that time wrote many of the Warhammer and 40K rulebooks and army books.
I listened to it over the weekend (mainly while doing a lot of cleaning around my flat) and it's pretty fascinating. Gav talks about how he got into wargaming and how he was given the job at Workshop (he literally handed in some home-brew rules at a Games Day, was invited for an interview and asked if he could start "next week"!) However, it's his description of how the Studio works that's most interesting. He recounts how it's structured, how decisions are made and how the R&D systems changed over the years.
He's now working as a freelance writer and explains about the trials of writing fantasy fiction and the differences in penning books for print and audio release.
The interview is here and Gav's blog is here.