From the 2006 documentary for New Beginnings.

Matthew gave up acting on TV after Doctor Who and concentrated on theatre. He has been living in the United States since 1998, currently in Connecticut, where he shares his home with his American boyfriend. He continues to enjoy performing on stage, and collects rare books by obscure mid-century poets. He visits England often, and appears at Doctor Who fan conventions in Britain and the USA.

In 2006, Matthew self-published his debut novel, Fates, Flowers. The Amazon.com review of it is as follows:-

Description:

Sara Smith is one of the most monstrous characters you could hope to meet. She lives in Greenwich Village on Life Insurance courtesy of her late husband, but she has fallen into a dreary routine: work in a card shop by day, where she is the rudest sales clerk imaginable, and weary evenings passed in the same cellar bar night after night with the same old people. But when she meets and seduces a gorgeous boy called Steve, she has no idea what she is getting herself into. Neither has he. Neither will you. Imagine a John Waters movie filtered through Edgar Allan Poe, with a touch of Mark Twain and a soupcon of the old English comedy of manners... The funniest, blackest entertainment you will read all year, as bracing and enjoyable as eating chunks of dark chocolate dipped in whiskey! MATTHEW WATERHOUSE has worked extensively as an actor in theatre and for the BBC. He is best known for two years as a travelling companion of the BBC's 'Doctor Who.' This is his first novel.

With Sarah Sutton, Peter Davison and Janet Fielding Recording Earthshock Commentary

With Peter Moffat, Sarah Sutton, Peter Davison and Janet Fielding Recording Visitation Commentary

At A Collector's Fair