Was looking at another site and found this link to old and new slang for paraffin heads and others who like diesels.
http://en.wikipedia.org/wiki/List_of_UK_railfan_jargon
Perhaps the Pacer should be known as a bog rather than a bug, unless the term bug refers to the presence of fellow travellers (insects).
Origins of 'bugs', Duffs, My Lordz....
this site also provides some information about 'modern' slang or jargon, my lords...
http://www.dreadful.org.uk/start.htm
http://www.dreadful.org.uk/start.htm