Ok, firstly feel free to give me an e-maul for a smart-arse comment... I take digital photos of stuff I'm returning, which always helps resolve these problems (OW, too hard!).
OK, it sounds to me like you have acted reasonably, and asked them to rectify a fault. In doing so, they have a duty of care to look after your equipment. They have not!
I believe that Jon Naylor is the Customer Service Director of DSG group, of which The Tech Guys is a part. You should be able to write to him at
Make it recorded delivery. (I haven't an email, but print is probably better). Explain the problem in detail (but if possible, not at length!). Ask him to intervene to resolve the problem.
I'm sure you'll get some more sensible advice posted as well. Consumer Direct may well be able to advise