Eddie - it's contained in the British Transport Films collection volume 2 "See Britain by Train"
These DVD's (there are 5 of them so far) are thoroughly recommended, even if you aren't particularly a train buff. They portray Britain of the 1950's to the 1970's and are put together with loving care.
See Amazon.co.uk: British Transport Films Collection - Vol. 2 - See Britain By Train : DVD