Certainly, if someone was was travelling across from Yourkshire or Suffolk, Norfolk or Lincolnshire or even across from the Midlands, the Harwich / Hook of Holland crossing might well be the ‘best’ way to go. It’s then about 220 miles direct (fastest) route from the Dutch ferry terminal to say, Gerolstein, to use the example in post #1.
From London, Kent or Sussex, I’d guess the ‘best’ route is via the Chunnel, from where it’s about 260 miles to Gerolstein, using the fastest direct route.
Broadly speaking, it’s six and two threes, depending on where you start from, time and, not least, cost. Those in Cornwall, have got a longer treck.
Once you are there, indeed the whole of that part of Germany and / or into Luxembourg / Belgium opens up for you. You can’t go far wrong in any direction. Take a short break or spend longer, it’s pretty easy either way.