I finally found that I had to start with the beginning.
Since I want that anybody can read my tutorials and find something of interest in them, going into the uvmapping of Vidigiani P-40 subsurfed model was just too involved for most people for a first contact.
The general index for all the tutorial is at http://membres.lycos.fr/bobois/index_anglais.html .
Look for the last entry in the tutorial list : it’s the uvmapping tutorial.
These four pages are not half bad as they are. They make for a nice, kind introduction I believe, as I left out most of the technical jargon ; yet, at the end of page four, just anyone should be able to uvmap a cube face by face and get a nice result. Of course there is more to come.
Nevertheless I absolutely need your help. I need you to tell me what points are still sticking (especially if you are new to Blender), if you were able to complete the tutorial, if some of my English is too puzzling to understand, if there are missing, misspelled words or if you found some funny typo.
Even more importantly : I need you to tell me what you want to see in such a tutorial and what gives you the most trouble.
Thank you all.