Ok much simpler guide (will have this on the website later)
This is a MK3 half first half second coach, the first class section is on the left and always at the country end of the train regardless of destination. The seat in yellow is a standard class seat facing towards Dublin regardless of the journey
This is a MK4 standard class coach, coaches C through to H. The seat in yellow is a standard class seat facing towards Dublin regardless of the journey. Notice the airline style seating mid coach thats the simplest way to know
Will have more later