Re: The Samsung Mobile - if you do not take out additional insurance coverage on the mobile phone, then your guarantee is in the hands of Samsung. Argos complied with this by sending your mobile off for repair (the same thing has happened to me with a Sony Ericcson mobile). If the technicians at the repair facility determine that the mobile was damaged through the fault of the owner, then you have violated the guarantee, which only covers faults which develop due to the phone itself. The fact that they request payment for repair indicates that they have determined that the phone was damaged due to the user. Sorry, but you must have inadvertently broke it yourself - not covered by manufacturer warranty!
So, to answer your question - a guarantee covers faults which develop in products without any fault on the part of the user. If you still claim that the phone was not damaged by yourself, I would suggest paying for an independent evaluation - and, if they agree with you, then claim the money and repair costs from Samsung. Hope this helps!
Ps. Not meaning to be smarmy but... they fixed my phone.