Hi Matthew, Welcome to “Old Time Lorries” on Trucknet. Dave a.k.a. “xkopite” has a good knowledge
of Liverpool lorries, you can find him on this thread in the earlier pages. Send him a PM (Private Message)
from this thread, he may have some knowledge and possibly some pictures of Williamson lorries.
Perhaps some of your relatives may have some pictures in a shoebox gathering dust in the attic. 
Kind Regards, Ray Smyth.