Since I have been mentioned by Ausclassics I feel I must do as requested, and clarify the final outcome of my complaint.
When I contacted ******, they had no explanation for the "missing order" but accepted that they had the money for it and would make good. They asked me to provide them with carpet templates for my car so that they could make some for me - suggesting that in fact they had never made any.
Subsequently I got what I had ordered (eventually) but only because I went to them directly. Stuart/Ausclassics never contacted me again, ever.
As for the claim that the mats were "found at Australia Post" - that is news to me. I had to wait for new mats to be made at my request. There was never any suggestion to me that any delivery had been "found".
He may be correct that only some of his deals went so sour, but he never made the slightest effort to fix the problem in my own case, so it is easy to understand the bad publicity around his business.
Verdict: going to forums and getting real life feedback on suppliers is well worth doing if you have any doubts. The measure of customer service is how suppliers respond to problems; anyone can do a decent job when everything goes right. Not responding at all is a sure sign of poor service.