Atrocious service and equipment

We had the unfortunate displeasure of purchasing a Gentech pressure washer. We bought it through builders warehouse online platform and received it in what we thought was good order. After using the machine for the first time, we noticed fuel leakage and saw that the fuel tank was cracked. Although this fell within 6 months of the purchase, the machine was sent off for repair; as opposed to being issued a new one and returned to us. Upon receiving the machine we saw that fuel tank was replaced but the fuel pipe was bent hindering the flow. In addition to this, the exhaust was falling off and the fuel tank was fixed at an angle on the bracket. Off it went again for repair and was again return "repaired". We opened the box and checked that everything was in order and it seemed to be. A few months later we decided to use the machine and whilst using it for a few minutes the exhaust burned entire off the unit. We unfortunately hadn't had time to sort this matter out and yesterday finally sent an email regarding the matter. I received a call today and when I stipulated that this was now the third time this machine is going in due to being defective, therefore we require a full refund, I was told that won't happen. We've used this machine 3 times and every single time it had an issue, when do we have actual use of the machine if it's always going back and forth between repair and garage. Builders warehouse have stopped selling this product and I'm glad they have, a reputable company should never sell defective stock to the consumer. There is apparently no one higher up that can be spoken to regarding the matter, isn't that just convenient, and when I mention the CPA the technician Cam counts it as a threat and goes on a rant, unfortunately for him I can also shout. I would like for someone to call me who can explain why we cannot get our hard earned money back. We've been told that someone would be here to uplift the unit, we have not agreed to this so I also can't understand why any of our information is now being distributed to a courier company without us giving the go ahead. This is the most difficult company we've ever had to deal with.