At long last I have obtained a catalogue from J T Batchelor of Islington. It's in the form of three pdf files - Tools, Buckles and Dyes - but the files are too large to upload onto the Forum.
It doesn't have prices, and neither does it detail the leathers that they stock, but it lists the items that are available in each of the three categories - a step in the right direction!
If anyone would like a copy, PM me with your email address, and I'll gladly forward the files to you.