Hugo
Thanks for your kind comment! I thought I had posted something on the boundaries some time ago.
There is an excellent site maintained by National Library of Wales which has the Tithe Maps easily navigable plus overlays of current and old OS maps. It's quite fascinating and you can easily spend hours surfing the details including field names, land ownership and lessees.
You can find it by Googling Tithe Maps of Wales. It is split into (Ecclesiastical) parishes so boundaries are fairly clear.
I did ponder the strip along the front linking the town with Penrhynside and Little Orme. Initially I thought it was a Mostyn inlfuence but am not now sure of this. Chris Draper's 1200 plan obviously pre-dates any Mostyn activity in the area and the two Mostyn seats, Bodysgallen and Gloddaeth, were both in the Parish of Llanrhos or Eglwysrhos rather than Llandudno. I wonder if the strange boundary has more to do with the Manor of Gogarth rather than Mostyn per se. I will have to do some more research on this.
Incidentally, the C19th 25"/mile OS maps show most of the boundary stones clearly.