I have found this topic fascinating and wish all the modellers concerned the best with their efforts. I would like to add my own contribution, based on studying GNR(I) architecture. The trainshed in Great Victoria Street was a carbon copy of that in Dublin Connolly so to build the former the latter is worth studying. This applies with the columns and beams. The columns supporting the canopies at the end of the trainshed are the same as those in Malahide and Lisburn (Up platform),so these stations canopies are worth studying. These stations also have the GNR(I) polychrome brick architecture of W H Mills. The signal cabin is a stretched version of the standard GNR(I) design.
If anybody has any further questions, I would be glad to help.