Rail/Sail ferry and train

This one is a bit clearer as to what you mean. You can probably delete the other post in Ireland to tidy up and save duplicating threads.

The easiest way to do this journey is to take the train to Birmingham New Street, change there for a Cross Country train direct to Southampton. That way you avoid the cross London transfer.

You could even go Holyhead to Newport (Gwent) on a Transport for Wales train, then Newport to Southampton on the hourly Great Western trains service.

The best and by far the cheapest way to ticket this journey is with a rail-sail ticket from Dublin to Southampton- boat and train inclusive.

This is available both on the Irish Ferries and the Stena Line sailings.

Any of the above routes are valid on sail-rail, and don't have to be reserved ahead. Just decide on the day if you want.

Re your other post the "problems" of Avanti are heavily over stated. Apart from anything else Avanti are using their newest train sets- the Evoras- on this route. Also, especially if routed via Birmingham, you are as likely to be on a Transport for Wales train as you are on Avanti.

EDITED- The through fare is £57.50 including the ferry a fully flexible ticket. Currently none of the 3 bookable routes to Southampton are via London. They are-
1- Transport for Wales to Chester, Avanti to Stafford (an easy station to change at), Cross Country Stafford to Southampton arrive 1645
2- TfW/GWR as above via Newport, arrive 1802
3- Transport for Wales to Wolverhampton (another easy station to change at), Cross Country Wolverhampton to Southampton, arrive 1842.

The ferry fare alone would be 48.50Euro so effectively you are paying about £15 for a fully flexible train ticket from Holyhead to Southampton if booked as a sail rail package.

In no way am I trying to dissuade the OP, this is exactly the sort of journey I'd make myself, but with the ferry and train journeys together be aware that from Dublin to Southampton is approximately 8-10 hours. I Absolutely enjoy sail-rail options and when I did Irish Ferries from Dublin to Ironbridge years ago I did pay up for the Club Class Lounge on the ferry.

Thanks all for your insights.
Using the sail/rail package would it be acceptable to spend a night in Holyhead before proceeding to Southampton via train the next morning?

Great questions that I don’t know the answer to, except to say I took the Irish Ferries trip Dublin to Holyhead last month and enjoyed it. Plenty of comfy seats, easy on and off. There was a bus from the ferry to the terminal building in Holyhead and the train was right there (but not a lot else).

That is a really interesting question about a break of journey.

Firstly, to be frankly honest, as Texas Travel Mom alluded to, Holyhead has not a lot to want to stop over for unless you are going to go round to the South Stack Lighthouse or visit the lovely Holyhead Breakwater Country Park (the breakwater being why Holyhead is now a ferry port, going back to 19th century stone extraction). But, shh, that's our little secret.

Or the Penrhos Country Park (even better than Breakwater) , out towards Valley.

Secondly, unless you run out of trains, you are not allowed to break your journey overnight.

Thus on the morning and lunchtime boats you have to keep going as you don't run out of connections.

The evening ferry at 2055, arrives 0020 no longer has a boat train connection. So in that case you can. I highly suggest the Travelodge- straight outside the Port. I don't know of anywhere else in town which is decent and apologise to any local guest house owners if I am doing you a dis-service in saying that.

TfW is only giving me Irish Ferries connections currently, but Stena is much the same, almost identical times.