Hey Karl
Maybe Stephan can help you on this, as he came in Ireland this year, pretty much the same way you show on your map.
As for me, each time I went to the continent, I took only one ferry to Cherbourg... You have to check both possibilities, but I think all in all, you have less driving at the end taking only one ferry, but the ferry journey last 20 hours !
You save on driving, but not necessarely on time ! And with my great organisation :lol: I prefer to deal with only one ferry (yep, one year, missed the ferry by... 24 hours!
)
You basically lose 4 days on your week, just for the travel...
Is it worth it ? Well, each time I drove 2 days to go to Retroplane, that was totally worth it at the end !