Thanks folks.
Have decided to go via Sens to have a look at the very first Gothic cathedral ever built - yes, I actually like that sort of thing! That will involve a bit of A104.
And return via Rambouillet to revisit a much nicer chateau than the one down the road at Versailles (IMHO) then via Beauvais to Zeebrugge.
Opinions sought. Opinions garnered. Decision made. Thanks given.
Case closed.