Doctor Who 60s book

It's Chritsmas, 1963, when six-year-old Gerald starts playing a new game: 'Daleks'. It's a game full of dangers and daring and terrible, mutated montsers. Gerald's parents think it's harmless at first. But then things start getting out of hand, as Gerald inists there are yetis in the basement, and Cybermen invading London. Desperate for help, what Gerald's family really need, right now, is a Doctor.