If anyone is interested in buying it, a book on the subject entitled.....'United Towing 1920-1990' by Alan Ford may still be available. Its ISBN is 1-872167-07
Printed by Hutton Press Ltd, 130 Canada Drive, Cherry Burton, Beverley, North Humberside, HU17 7SB.
The publishers were Clifford Ward &Co, 55 West St., Bridlington YO15 3DZ.
I don't know whether it's still in print as I bought my copy in Hull some time ago.
Hope this helps.....................