Simply Awesome.
Having grown up here in north wales, i always thought these stations might make a good set of models. If done covering a period that had lots more traffic than now, all the freights gone :-(
You seem to be getting along nicely. This book http://www.amazon.co.uk/Historical-Chester-Holyhead-Railway-Track-Illustrations/dp/B001MWNG74 is very useful for full track diagrams and signaling information.
I haven't found anything concrete about traffic during the 1950's-60s but the 70s this sight seems good http://www.2d53.co.uk/links.htm One thing i do know is, tales from grandparents, The port of Holyhead exported\imported massive amounts of livestock to and from Ireland, mostly cattle. Hope that helps
Welsh_Rob