Ray, I can help with some of this but you will need a local chartered accountant to answer some tax questions for you. I know nothing of that side of the POND
Yes, insurance is a very good reason to value your equipment tools and inventory.
Let's start with definitions and I would want to seperate equipment and tools from INVENTORY.
Inventory, to my thinking and experience is best left to supplies and raw goods used in the production of property for sale.
Leather, thread, maybe lasts, definitely dyes and glue and nails and pegs et. etc. etc.
Tools do not of necessity get USED UP in the manufacturing process.
The same is true equipment.
Again I do not know of the tax ramifications on those types of items.
Especially for insurance you need a record of those items to justify a claim, if needed. We recently had a member in Florida lose his tools and everything else in his barn from a fire. My God what would it cost to replace my Barnsley, Rose eTC. knives, Cases of Misc. tools and buckles. No insurance company would take my WORD for it all.
Equipment is easier I thin and should be maintained on its replacement value for insurance, if you can afford that.
So let's call inventory supplies and raw goods.
To simplify I would suggest you divide your items into "A,B and maybe C" items. Expensive leathers, full spools of thread, full bottles of dye ETC. are "A" and will be measured carefully and valued. Next are quantities of say rivets and buckles and needles etc. that are "B"s and any good effort method of valuing will do.
Last are open bottles of glue dye shoestrings etc. I hold up my thumb and SAY....about $one thousand or so. If that amount does not change much overt the years, and it shouldn't. Don't count it carefully.
Gotta go for now. be back later
Kevin