This is the second thread I've seen recently where a customer has come here with a massive description of perceived poor customer service or product by large manufacturers. On first reading these (and I admit it may not be merited at all), my default setting is to side right with the manufacturers. I understand that in some or even many cases, it's exactly as the customer described. But right off the bat, my spidey senses start to tingle. Maybe because I used to work in shops, and have seen irrational customers and their demands first-hand.
Maybe if the OP had started out with something like, "I had some problems recently (which I can go into later) with Merlin/DEAN/Janus Cycle Group. Has anyone else had problems dealing with them?"
But to come out with the topic "BEWARE - ..." just kind of puts me on the defensive right away.