Hi Junctionmad,
Your layout plan for Limerick Junction is excellent, would be a serious amount of work if you went down the 21mm route.
I started Nenagh in OO with Peco 100 track and got to a near complete layout before taking the plunge into 21mm. EM is
a good option, at least you can buy the track in 1 metre lengths, but either way I recommend you use a finescale track.
Are you able to see the rest of my photo's in the Album section of this site? You should be able to copy and zoom in on the
details of the C10. Slide chairs are used but cut in two and used cosmetically.