There are vans that deliver furniture for people moving to and from the UK through the channel tunnel. Don’t tell them it’s a skateboard and they’ll never know
Only problem is I don’t know how they work now that UK has left the EU… maybe they inspect things and ask for import tax 
how do i find those vans online?
yes, they want tax now.
But if you would have a skateboard in the back of your car as sports-gear… ?
Google or Bing 
Thank you @BigBen for sharing the contact of a nice transport guy.
I am in contact with him and it seems to work out perfectly.
He is doing the transport for 150€ on the landway with a truck. Good deal for me.
If anyone else needs a transport service for transporting things on the landway from UK Island, drop me a message and I will share the contact details.