Heh, thanks all.
In the end plans changed about 2 mins after my first post, and I’ve come back on the plane today. Emergency paperwork being picked up 10am tomorrow, (Tuesday) and he’s on a teatime fast-ferry on Wednesday from Cherbourg, which splits a very long drive into 2 sensible portions. Stop over on Wednesday evening with a pal in Hampshire and back home on Thursday.
I do now wonder what would have happened if we just rocked up at the ferry port with one passport and a pair of driving licence ID’s between us, but I don’t think he’d have liked that risk.
Turned into a bloody expensive ‘week’ (damn near two actually).