National Museum of Northern Ireland: Here is a copy of what they sent me.
Images from our collections can be viewed online and prints can also be purchased for personal use only:
A charge of £50.00 + VAT to £75.00 + VAT per image will be made for the scanning of a plan when a digital copy is not in existence.
Note: They said that Low Resolutions are usually done for free (I highlighted in yellow in attachment so you can determine what you want). You will have to fill out a 'Ship Plan Enquiry Form' attached. They take quite awhile to get in contact with, and to reply. You want plan
Which is the Line Plan
Hope this helps