I've been across the Pond numerous times on Int'l Tech Biz, and pals there have various Rigs. Along with direct observation on LOTS of miles traveled while being shuttled to Customer Sites as 'The Tech Answer Man', and at Autobahn-side 'Petrol' Stations, here's my observations.
1. Work from some assumptions backwards. By that, I mean that many Europeans Camp. They don't ruin their Vehicles doing so. Therefore, the Rig towed [or driven] is down-sized appropriately. Indeed, German pals I hosted years ago just laughed out loud when they first saw a Crew Cab, Long Bed Diesel here wondering 'what private Citizen could POSSIBLY need a Truck that large'? Or, the Parking Lot req'd to park such a Vehicle? It's fun to 'see' America through the Eyes of others. All our choices in Supermarkets of the SAME Products also blew them away. But, these friends were from the 'former GDR' [East Germany].
2. A Passat, as my Wife drives, is plenty of TV for Rigs sized to be towed by what the local Market owns [like Passats]. So, you see the veritable ton of VERY sleek Trailers, like down-sized versions of the 'Award' Trailer out of Canada w/a sloped front. Those Rigs clip down the Autobahn quite nicely and quickly. Larger-Engine Autos tow larger Rigs; no question that they're out there...
As mentioned here in a recent Thread, U.S. Automakers are de-rating TV Tow Specs. Log onto Euro Vehicle Sites to read what 'the real' Specs are, and what various Trailers there weigh.
Award Trailers
3. The Ferry System, which I've been on a lot, is like our Interstate Highways on the Water. There are MANY Routes, and fixed Timetables. They're a blast, especially over open Ocean where large Semis park downstairs and the Truckers can cut loose for the evening. We've driven a rented Class B onto the Ferry, and fees are based on length. This is why Euro Scania Trucks, or Mitisubishi Trucks, have squat fronts that sit over the Engines. You can get more Cargo on a given-length Chassis. This same logic drives TT/RV Design. So, a ~5 or ~6 meter-long [~15' or ~18' ft.] Trailer is an 'affordable' platform for those designing Trailers. If they're 'too long', and too costly to take over to Scotland or to Denmark on a Ferry, the local Market will vote with their Wallets and not buy 'too long' a Trailer. Driving/Ferrying up to Sweden and beyond is a typical Holiday, usually taken in August when much of Europe 'shuts down' by Cultural convention.
P&O Ferries
I couldn't find a representative Euro Trailer Site just now to save me. Tricks I've learned, like going to the bottom of 'Yahoo' and then to the U.K. Yahoo Home Page, will turn up very different Search Results for items like <Camping Trailers>.
See a Scottish 'Caravan' Trailer Site here:
Scottish Caravan Club Site
Off-peak Season in May, we took our rented Class B to Sea-side spots and just about had the entire place to ourselves. Jockey the Dinette Window around to the Sea at a non-hookup [more remote] Site, and chow down on local Seafood and anything you'd want from the ubiquitous 'Safeway' [and other] Stores everywhere.
Roads are hilly and narrow, and there's a reason some fine U.S. Stock Car Drivers are from Scotland! When you learn to drive those Roads at high speed - the only way to get between many Towns - all on 'the wrong' side of the Road - you've cut your Driving Teeth on some serious Asphalt.
Campgrounds with and w/o Hookups are plentiful. Given a different attitude toward smaller Land masses, I've seen very nice Campgrounds during Roadside Lunch breaks that were reclaimed Gravel Pits. Showers are in Tin-Roof Buildings w/ambient Temps, so you learn to line up the Coins and keep the 'Demand' [Flash] Water Heaters going by plugging in Coins every 2 minutes or so. When the Water goes cold, it's REALLY cold! Yah, it's weird having a 230 VAC 'Flash' Electric Heater in the Shower Stall with you, but I got over it. Pray for good Grounding.
Some RV Campgrounds also have lil Cabins or Single Wide Trailers lined up for weekly Rental, not unlike the KOAs here with lil Cabins for rent.
For us Boondockers, even Laundry becomes a treat. Head into a Village, and have a fresh Scone and 'a Coffee' on a Park Bench while chatting up the Locals for conversations we remember to this day. Fly over Campgrounds and areas-of-interest on Google Earth to see Road elevations, and the lay of the Land.
Incredible fun, and World Class Beachcombing! And, super-friendly folks where you don't ever have to think about getting mugged or hassled. Especially on the North Isles of Scotland, like 'Orkney', folks in everything from Tents to nice RVs take the ~18 hour Ferry Ride over from Norway. Take about a great way to meet people! The Film 'Local Hero' turned us on to Scotland in particular; highly recommended. We visited all the Filming locations in our rented Class B.