The thing with it was - it wouldn't support even stock clocks after the cable extension was used, suggesting the cable supplied by QuietPC had fried the board. (QuietPC didn't supply the CPU/board - only the faulty cable extension and are therefore liable for damage caused by it).
So why was the situation confused by insisting they test the OC ? Surely it would have been better to just say after fitting the cable extension my system no longer runs at the correct speed, even after swapping back to my old cable. I always find when communicating with company's about faulty product its best to keep it simple and try to sum up what the problem is in once sentence, if they need more info they ask for it.
If this was the case that's all that was needed to be asked of them, just to run it at stock. Asking for other things just confuses things/won't help the cause surely?
I've come back to this and here's my recommendation. 1. Ask quietPC to test at standard spec 2. If it passes - great, you get your kit back and we move on. If it fails, you can ask them to replace or offer ££ to the value to replace. 3. ???? 4. Profit