A lot of sellers on eBay, have Military releated items for sale, myself included.
What you have to remember is that 99% of the Issue items are issued to all members of the UK Forces, not just Special Forces.
It use to be the case that you could spot an issue bit of clothing or equipment, becuase it had a NSN Number, this is no longer the case, as a lot of companies that manufacture their goods in China, happen to put NSN Numbers into the items, this dosn't mean that the item is "issue" or that the NSN number will even be real.
There is another side to the military clothing and equipment market place - one that I fit into as much as other sellers.
UK, USA and European based Manufacturers - We design, manufacture and sell military clothing and equipment, that don't have NSN Numbers, and isn't normally an issue item, but can sometimes be a "local purchase item" - what does this mean? Well it means that a military unit has asked a company to produce an item, on a small manufacturing run, for issue to a small number of members of the forces.
An example of this is the Land Warrior Rifle vest that I manufacture, it was orignally designed by a member of UK Special Forces, and I was asked to re-design the basic vest, upgrade and then manufacture and sell it. - The first run of this vest, were all sold to members of UK Forces. - So while not an issue item, it was used as issue by members of the UK Forces.
Next look out for IRR treated items - now if you happen to be serving in operational zones, you require your kit to have an IRR coating, a lot of items are manufactured for the Airsoft market place, and as such have no IRR in them. But as soon as you get any bit of kit or clothing dirty, it gives it a IRR coating.
Well thats it for now.