Gentlemen
Many thanks indeed for your time and information - its like a potted master-class in airways flying. Bfisk's summary gives me a much better over-view of modern nav and I found the web-sites suggested a mine of information.
Bookworms comments make much more sense of the airways chart I have just acquired.
I was amazed at the ROC/ROD's you mention, Denti. I had guessed at a max climb of 2000ft per min and to find that it may be more than twice as much is a real surprise although I appreciate that it will decrease with altitude.
I really am obliged to you, I now have a far greater understanding of modern nav. To me this is what PPrune is all about.