eBay's dispute processes are bot-driven. There are certain criteria which will lead the dispute down a particular automatic pathway.
There's no doubt that buyers have far more power than sellers, and that the burden of proof is ridiculously placed upon the seller's shoulders to the extent that in some cases, it's impossible to prove to eBay what they would need to have proved in order to rule in the seller's favour.
However, there are certainly things that sellers can do to protect themselves.
To prevent a claim of an item not having arrived, send by a trackable method where proof of delivery can be shown. (Under eBay's MBG, proof of delivery is required rather than proof of postage. PayPal's burden of proof of lower - it's proof of postage that is required for them.)
If you can't justify the cost of signature on delivery (proof of delivery), then self-insure. That means that you can cover the cost of the inevitable claims that an item hasn't arrived. Work out how many claims are made per year, the cost of the items, the total per year that such claims cost you, and then divide that by the total number of sales you make on average per year. That will give you the extra amount you should charge for postage to self-insure.
Keep excellent records. Sometimes you can go over eBay's head by talking to PayPal and demonstrating that you have sent an item based on your meticulously-kept records incl tracking number. If you have to take it to the FOS, those records will demonstrate you have a proven track record of sending items in a timely fashion, complete with customer's name, suburb, weight of parcel, tracking number, etc.
To minimise claims of items not as described, take high-resolution photos, including some that you don't upload on the listing and which prove definitively the identification of the item. If you sell items with serial numbers, always keep a record and photo of those. Describe every defect in your listing; under-rate rather than over-rate.
You can choose whether or not to have returns accepted; I note that you have a return policy for change of mind saying 14 days... but I think eBay override that now. It's 30 or 60 days according to the Setting up your returns policy page. If you're not happy with that (and frankly, I can see why sellers would not like it), change to "No returns". Buyers can still request a return if there's a problem, but not if they just don't like the colour or have changed their minds for some reason.
Your listings offer Click and Collect. I'd get rid of that, as Click and Collect just means there's a third party involved, which more chances of something going wrong. What if the buyer doesn't get the SMS to pick up the item?: What if they never get the code? What if the staff at one of the supermarkets specified for click and collect doesn't know where the item is? Or the parcel's simply lost? Too much chance of things going wrong...
Well done.
