Cheers for the link @wombat. Did have a brief look on there, but that obviously involves buying the book. We have a gps and mapped a route using as many quieter country lanes as possible. In the ‘Guestbook’ someone has said to avoid the NCN 2 which is helpful to know.
@pete, we will be avoiding the a303 altogether. I regularly drive it to see my parents and would never consider riding it, especially with the 50mph winds we are expecting (as you rightly said).