Trains from Dublin Airport to Glasgow

You can take a bus from Dublin Airport to Belfast. I don't know whether the cat would be allowed on the bus. Otherwise, you can take a bus or taxi (if the cat isn't allowed on the bus) into the city to get the train to Belfast. Here is some info on the ferry and train between Belfast and Glasgow.
https://www.seat61.com/train-and-ferry-to-belfast.htm#via%20Cairnryan

Theres the added complication that authorities do not permit more than one flight a day for a pet.

Go to Heathrow and fly to Glasgow the next day?

Go the Heathrow and take the train to Glasgow?

Go to Belfast and fly to Glasgow the next day?

Put the cat in a cattery?

Get a friend to look after the cat?

Thank you Trelawny for the list of suggestions. I cannot fly to Heathrow from US because I cannot have my cat on a flight into UK at all. Same for Belfast. The reason that I am going through this rather tortuous process. Cannot afford cost of pet cargo from US to UK.

I do have a very kind friend to care for Pixel as back up. I prefer if I can, to bring him as he is very attached to me. I hand raised him from time I found him on side of highway. He was 3-5 days old. He has travelled by plane in cabin and by rail. Very experienced with travel and tolerates it well. Thanks again!

Thank you G3rryCee for the links and recommendations!
Very helpful!
Cheers!
Robin

Ferry Dublin to Holyhead, then train to Crewe, change, train to Glasgow is another route, more frequent than the once a day rail connected route via Cairnryan- the ferry to Cairnryan runs every 4 hours but only one sailing is rail connected.

On 13 May (you arrive early on 12 May) the ferry leaves Belfast Port at 1130, arrives at Cairnryan at 1352, a connecting bus leaves Cairnryan at 1415 for Ayr Station, arrive, transfer to train leaving at 1535, Glasgow Central arrive 1626.

On that route the ships have a dedicated pet lounge- https://www.stenaline.co.uk/guides/superfast-pet-lounge

To make the 1130 ferry you need to leave Dublin Connolly on the 0650 train, arrive Belfast Grand Central at 0858, then taxi to the port, or a bus #96 from Upper Queen Street at 0940.

From Dublin Port (taxi from the airport) you leave at 1015 to Holyhead (which is excessively tight) and arrive at Glasgow Central at 2113.

Or, on 13 May leave at 0430, arrive Glasgow at 1517, or at 0730, arrive Glasgow at 1801, or the 1015 as above.

However, and it is a big however, a pet has to comply with UK rules whether arriving by air or sea - please review the stena line rules for transport of pets on their ships- https://www.stenaline.co.uk/customer-service/pre-travel/can-i-bring-my-pet#iba

and these are the official UK rules- https://www.gov.uk/bring-pet-to-great-britain

Thank you isn31C for the great information!
My cat, Pixel is prepared for entry into UK and Ireland. He has his rabies vaccination & has been microchipped for years. The EU and the UK health certificates will be completed, signed and submitted by a USDA licensed vet who will examine him.

I don't have much more advice to offer beyond what's been said above, but just wanted to wish you good luck, as moving pets in and out of the UK is ridiculously complicated! The reason the UK is so strict (and won't allow pets in the cabin) is because rabies has been eradicated here for a very long time (easier to do when you're an island) and they understandably want to keep it that way. We've looked at bringing our dog across with us to Ireland and even that has been so complicated, expensive, and time consuming we haven't done it yet. Glad to hear you've had some professional advice on this and hope you and Pixel make it safely to Scotland!

isn31c's advice is the one to follow. Ferry to Holyhead, then train to Glasgow via Crewe.

It has been about a century now that the UK and Ireland have been rabies free. If you want to send a chill through a lot of people in those countries of a certain age, mention rabies. Our public information films were.... memorable.

To be fair most of our PIFs from that era were memorable, the rabies ones were extra disturbing.

Adding a link here to the requirements for bringing pets into Ireland, useful reference for future travellers: https://www.citizensinformation.ie/en/moving-country/moving-to-ireland/coming-to-live-in-ireland/bringing-pets-to-ireland/#fe283a

Many thanks to this great community!

To MC & Cat VH thanks to you both for your good wishes and some history of dreaded rabies in UK. I do respect the need for vigilance.

MC thanks also for confirming the advice to travel by train/ferry through Holyhead. Local and lived experience is the best advice!

FSS thank you for the link to requirements for bringing pets into Ireland. Much appreciated!