The Danger Men, by Nick Walters

Second paragraph of third chapter:

‘Sorry? Sorry?’ The other man looked at him as if he were insane. ‘Say what?’

Next in the sequence of Lethbridge-Stewart books, though this one barely features the Brigadier. Lethbridge-Stewart’s chum Bill Bishop is swept back in time to the distant days of 1999 and finds himself in the body of a British spy on a mission which may or may not be officially sanctioned. It’s well enough told, but has practically no connection with the Whoniverse, apart from references to concepts such as the beryllium clock (from The Movie). You can get it here.