What a research. Nicely choice for your Farthing Sidings.
I the past I had also a look at the railways at Glouchester.
Was interested in the railways around the docks.
For your general millage sidings I think you can find some useful information on this website: http://www.gloucesterdocks.me.uk
( noticed the link says page not found: click on home in that page and you will go to their home page)
Looking forward to your progress.
Regards,
Job