Ok another update. I send my REACH document to Amazon and got this response;
"A list of the ASINs has to be an integral part of the document. "
I make handmade jewellery using metals that have been REACH tested and have supplied the document evidencing this, but Amazon are stating that this is not enough, my actual finished product must be included in the REACH document. My items are made from REACH tested metals and nothing more, and thus Amazon are saying they will not trust the word of hand made sellers about what materials they use in their hand made products.
It will mean the end of selling at Amazon for many sellers who hand make products from metals that Amazon have deemed must have a testing certificate - for the final product, not just for the components.
Most small sellers cannot afford to REACH test their every single product made by hand, and so a lot of Amazon Handmade sellers will be shutting shop.
So far Amazon have told me that this only applies to copper, however I expect there is a chance they will extend this to other metals and this makes me not want to invest any more time or energy in listing new jewellery products on a marketplace that may remove my products on the basis of them not being REACH tested.