Diane Bell has written a novel called Forever Friends.

Finn Clark has written a number of Doctor Who-related books: the Time's Mosaic review series, so far covering Jon Pertwee, Peter Davison, Colin Baker, Christopher Eccleston (including Torchwood and Quatermass) and the first of two David Tennant volumes. He's also written Dalekese, a guide to the Dalek language as seen in TV episodes, books, comics, etc. He has a short story in the Ice Hot anthology, based on the worlds created by Stephen Wyatt in the TV story Paradise Towers.

(If you'd like to buy any of these books, click on their names above and you'll be taken to an appropriate page.)