Definitely a piece of string. Depends on winds. Not less than a few days, or more than ten, I would have thought, if you weren't stopping anywhere.

Remember that when the fleet was coming up the coast to pick up Moore's army at Corunna, it got stuck for several days around Vigo because it couldn't weather the cape. Of course they were going the other way.

I can't recall how long it took Wellington to make it from England (Portsmouth?) to Lisbon but I think people could sometimes do it in 10 days with good winds.

Cheers

C