Getting a courier from London to Brittany, circa 1478

Hello, all,

I'm in the midst of writing a novel of Richard's time, and I'm at a point where a courier from the King of Mann must travel swiftly from Edward's court in London to the Chateau de l'Hermine in Vannes in Brittany.

Would said courier be best advised to get a fast steed and make for Southampton to hitch a ride on a wine merchant's cog in order to cut a day or two off his travel time, or would he be better off just taking a ship from London, which would be a bigger port and far more likely to have a ship or two in the docks that was going to be sailing soon for Brittany?

Happy sailing,

Tamara