Surely the answer is staring you in the face?
You are presenting yourself as a private seller, but private sellers here are limited to selling their own, unwanted possessions.
You are currently listing about 250 all new fishing accessories, and you say you were making up to £500 a month here. Hasn't it struck you that you should be registered as a business seller?
Your buyers would then not have to pay eBay's buyer protection fee. You will be competing on equal terms with other business sellers, including paying eBay's business seller fees, which you are currently escaping by selling on a private account. But these should not be much more than you were paying before.
It's all explained here: https://www.ebay.co.uk/help/policies/selling-policies/selling-practices-policy/business-seller-polic...