Rudi: I'm affaid it would have to be the university of life.
But may I suggest you invest in "A dictionary of slang - an alphabetical history of colloquial, unorthodox, underground and vulgar English" by J.S. Farmer & W.E. Henley, published by Worsdsworth (ISBN: 1-85326-904-2). A bargain. Two volumes of fun and merriment for all the family and a bible for the scholar of the English language.
As a teaser I looked up a suitably apt entry, viz:
Swiss Admiral (naval) A pretender to naval rank. Fr. amiral suisse = a navel officer soley employed on shore, or who has never been to sea.
You won't find that in Collin's or the Oxford!
Nick
PS: Catman, whatever you do don't ever go into a pub and ask for "a pint of spotted dick"!! But thank-you, I haven't laughed so much for years. Simone and I are both in tears of laughter.