Route advice: Cherbourg to Vannes (esp. fuel stops)

[Basil Hume]

It seems that the ferry to Cherbourg (rather than St Malo) is more convenient for a trip in late August / early September 2015 to the countryside near Vannes.

It'll be my first drive with our family of four on board - in a Golf R32, which likes a drink...

Any general advice on the route (including fuel / "family" / wee stops) would be gratefully received.

[Basil Hume]

These are top tips, received with grateful thanks. More would be good, if anyone else cares to...

For better or worse, the trip is now booked via ferry from Poole to Cherbourg.