On a slightly different note, Andrew Smith - writer of Full Circle - was a big fan. This story was basically the first bit of fan fiction to make it to the screen.
The revived series has used many fans-turned-professional writers, such as Paul Cornell, Mark Gatiss, Gareth Roberts, Rob Shearman, and many others, including RTD and the Moff himself.
Back on track, I'm sure I read that Bernard Bresslaw was delighted to be cast as Varga as he loved the show. Although he thought that an Ice Warrior would look like a Viking with a bit of fake snow on top, and he was a little baffled when he was told to report to a fibreglass boat building company for his costume fitting...