Looking at your feedback transactions, you dont really have much to worry about. 

A paper trail for someone that is selling a large volume of items and then trying to say it is inherited will have a probate statement as to what it was valued at for tax purposes. If there is no probate it is deemed to have been valueless. If it is valueless there is no tax deduction available. So no paper trail and everything is taxable less costs.

If you are a collector, you will have purchased the item and that is where there is a receipt. This is in the instance of where someone sells a lot and it clearly looks like a business online. If you buy a big box of vinyls for example, as a job lot, and then sell off the ones you dont want you must allocate the cost of the purchase against the sales and declare. The Revebue may disagree with how you have allocated that cost but that is a after process after the initial assessment and all the paperwork available is produced.

Ignorance is no defence and either is not having paperwork.

Best to always do it properly, declare everything over the limits and there will be no problem. As I say, on your numbers of sales, I dont think you will have an issue.