A year or two back I used to drive roughly the route the OP is planning every couple of months for work. I had a fair bit more to do on the UK side than the OP and slightly less in Germany. Personally I prefer the tunnel to the ferry as it's quicker and less of a faff, not to mention less seasickness-inducing. It's a pleasant enough route overall, though not terribly exciting and the traffic on the motorways in Belgium can get a bit M25-like.
The "coolest" road trip I've done by car was about 6000 miles around Europe in a '74 Beetle which was about 15 years old at the time. The route started in the UK, across to Ostend, through Belgium and Holland to Münster in north Germany, down to south Germany dipping into Austria and Switzerland, then right across the middle of France and the north of Spain to Salamanca, diagonally across Spain to Murcia, across the south of Spain to Seville, then right across Spain and France again back to south Germany before finally heading back to the UK through Luxembourg and France. The whole trip took the best part of a couple of months. It wasn't all driving as I spent quite a bit of time in some of the places once I got there, but I did drive for 18 hours at a stretch on one occasion stopping only for fuel, food and the like. Incidentally I don't recommend driving for that long in one go; it wasn't a particularly pleasant experience.
My limit now is the 12-13 hour drive from where I live down to the Alps, which I do (or did until recently) a couple of times a year.