Travel from Dublin to London by Ferry and Train

That should be the last day of the emergency ferry timetable meaning that ferry to rail connections are not as slick as normal.
The ferries are rock steady and sail in almost all weather. That was what caused the port closure in December - the ship sailed, but then was blown on to the quay when trying to dock.
Stena sail from Dublin at 1010, arriving at Holyhead at 1345, in good time by chance for the 1448 Avanti train direct to Euston.
Frustratingly you can only book the money saving sail rail deal in that direction on line using Irish Ferries - 0745 from Dublin, arrive Holyhead 1110, depart by direct Avanti train to Euston at 1248. Also buy from Dublin Heuston or Connolly stations until the last minute.
Note it can be bought on line, but has to be mailed to you.
That will save a lot of money.

We did the trip the other way - from London to Wales to Dublin. It was all fantastic, but I find those unique modes of transportation to be part of the journey. Some people may think otherwise.

For anyone going the London to Dublin, the hitch in that trip was the very end... Just no cabs at the terminal to get into town... Okay, we'll a few cabs, but it was a loooonnnnggg wait.

Here is the Man in Seat 61's info, including photos and videos.
https://www.seat61.com/train-and-ferry-to-dublin.htm

In 2010, I took a similar trip: a ferry from Cork, Ireland, to Swansea, Wales, and then a train to London. (I believe that route might have been discontinued since, but the ferries from Dublin to Hollyhead and other places are still running.) The ride was perfectly fine. The ferry took off at 8 pm and arrived in Swansea at 6 am. I got a cabin for the night.

A blast from the past with the long gone Swansea to Cork service. Good route and good ship. At least the ship is still in service on sailings to Corsica.
A proper overnight service, rather than sailing from Pembroke or Fishguard in the early hours of the morning.