Route des Grande Alpes

[Spud 7]

Having now got a bit of a bug for travelling on the bike, myself and a friend are planning doing the Grande Alpes route next year.
We live in the North West of England, and as this will be our first continental tour, we've come up with a few questions. Hopefully someone will have previous experience and be able to help us out.
To actually get across the Channel, would people recommend riding down to Dover (a days ride realistically) and getting a ferry from there.
Or a few hours hop across to Hull for the overnight ferry down to Zeebrugge or Rotterdam?
Also, as the route starts in Geneva, is there an easy way to get down there? For example a motorail service, or do you just bite the bullet and ride down?
We are limited to about 16 days in total for the trip and obviously don't want to be spending large amounts of time on Motorways, mindlessly chomping off miles.
Also, as this route takes in part of Switzerland, would a carnet be required at any stage?
Any suggestions or comments gratefully received.
Thanks