Here's some more pictures of the area that I've found on Flickr.
31 159 on the Motorail shunt at London Kings Cross. 25/05/85. by Adrian Nicholls, on Flickr
Class 31, Kings Cross by nigelmenzies, on Flickr
Kings Cross platform 9 3/4 by David Flett, on Flickr
Classes 31 and 47 Kings Cross Loco Jul75-p18masfdqk1mo37j3dckocc82t by Alan Rintoul, on Flickr
Kings Cross Parcel Sidings by Warsop 37, on Flickr
gb_760811_31407KX copy by MUTTLEY'S PIX, on Flickr
31xxx | Kings Cross [1983-002-005] by Brian McCulloch, on Flickr
Kings Cross Interregnum by brentford40, on Flickr
Peak, Kings X by Will Welch, on Flickr
Kings Cross 7 September 1976 by davelindsell, on Flickr