Yes, great photo. This building must have been demolished sometime between August 1970 and early 1973, as it was in 1973 that I became a ticket clerk at the station - and I'm sure it wasn't there then.
Does anyone remember the old ticket office? It was located inside the current entrance hall, roughly where the automatic ticket barriers are now. People used to buy tickets from windows on either side (east and west) of it. It would be great to see a photo of that (if one exists).
There used to be an old unused room where the current ticket office is, and today's coffee shop is where the ticket collectors used to have their room (for keeping warm, drinking coffee, etc and playing darts). And... a bloke used to sell newspapers from a small booth just at the front of the entrance hall.
Lastly, does anyone remember the old ticket clerk called Bill? He had a wooden leg and had been at the station for decades.