On every purchase you are given a date for delivery, it is slso shown before you buy, if within the UK it would be only a few days. If the delivery time is long, then warning bells should ring and you should buy from a better seller.
As soon as past the expected delivery date, then you can open a not received case,and if seller does not refund you escalate to ebay who will.
Far simpler to use the tools already in place to get a refund, than quoting rules that are difficult to enforce. What you should do is leave appropriate feedback as a warning for others.
