Dublin -> Holyhead is *much* more civilised during the day. You can get a cat instead of a big ferry, so it's a <2hr crossing, and the trains at the other end are pretty sensible. Also, depending on where you're coming from, you can get a ferry from DĂșn Laoghaire, which is small and civilised and truck-free. I hate the cycle ride into Dublin ferryport.
no subject