Travel from UK by Ferry
Which ferry route & which ferry company had you in mind for getting to Cuxhaven, assumin from UK?
There used to be a ferry from Harwich to Cuxhaven operated by DFDS Seaways, but I believe this service has ceased.
Alternatives that I believe get you closest:
Stena Line: Harwich to Hook of Holland,
DFDS Newcastle to Ijmuiden (Amsterdam),
P & O Hull to Rotterdam
According Bing/Multimap all involve ~ 350 miles driving, 6 - 6.5 Hours!!
These are the 'light traffic times!!
The fastest times given by Google & Multimap-Bing are for no traffic, & assume every road on the route is driven at the maximum allowed speed for a car!!
Not a car towing an unbraked trailer, the legal limit for which, like the UK might be lower; how much for each of: France, Belgium, Holland & Germany I don't know.
Reality, with breaks and allowing for traffic around major cities will add at least an hour to that.
I lived in The Netherlands for 5 years & used the Newcastle <-> Ijmuiden, Harwich <-> Hook of Holland, & Dover <-> Calais ferries.
Found:-
Dover <-> Calais: Add 3 hours travel time to Harwich Hook & Newcastle Ijmuiden drive times.
Taking the Harwich & Newcastle overnight ferries meant arriving early morning refreshed ready for a full day.
There are a number of potential traffic pinch points:-
From Calais:
Antwerp Ring, alternative is Brussels Ring - both can have heavy traffic any time.
Where the A10/E40 joins the A14/E17 near Ghent, Belgium. I've been held-up here for nearly an hour on a Sunday evening in the summer. It's the main road from the Belgian coast to the capital Brussels, and on sunny a weekend in summer traffic was very heavy.
From Hook of Holland:
The motorway across the North side of Rotterdam experienced heavy start-stop traffic mornings & late afternoons the working days we took this route; weekends were better.
By contrast the motorway along the south side also carries heavy traffic, but every workday morning I used it the traffic flowed freely.
From the Hook take the A4 Bennelux Tunnel to get south side.
The P & O Hull Rotterdam ferry docks south side.
From Ijmuiden:
Going south round Amsterdam on the A9 Ring was stop start on the two Monday mornings we went this way.
It might be better to head north on the A22 -> A9 then take the provincial roads across to the A7, about 10KM, that then head up across the dyke separating the Ijsselmeer from the North Sea
My experience driving in Germany is motorway traffic around major cities can be heavy; Hamburg, which is on most routes to Travemunde, could be similar.
Travemunde dates collide with start of summer break for some UK schools, when I checked last week:
DFDS showed a massive charge, £270, for taking a boat size trailer out; compare with £74 for the car, & £60 for the return.
Stena are already flagging limited availability on some Harwich sailings.
I hope this helps with journey planning.
I've already concluded it might be better to double up: sharing ferry costs & the driving.