According to the websites here is the proposed schedule:
10:00-12:16 Dublin to Belfast
12:51-14:11 Belfast to Coleraine
14:20-14:30 Coleraine to Portrush
Will this work? Is the time in Belfast too short to make it from one train to the next?
Can we buy train tickets in advance for the Belfast to Coleraine and the Coleraine to Portrush journeys? Is it possible to reserve seats on these trains in advance as well?