We have cycled from Hook of Holland via Bruges, Ghent, Tournai, Mons, Namur, Reims, Chalons en Chanpagne, Brienne, Tonnerre to the Vezelay route. See our blog for details. I think there is a more direct route from Amsterdam which takes you east and to the Meuse at Maastricht. In France the GR654 goes from the border at Dinant to Vezelay (and beyond).
Ivor, do you think it would be a good idea to have a sub-forum for the extra long pilgrimages which begin before the four French routes?