Do any of the major PSU manufacturer guarantees also cover damage to other PC components? I'm sure I read someone post something suggesting that some did a while ago...
If you bought the item yourself, this is important, then you can claim the damage caused to your property by an unsafe product from the trader or the manufacturer. If you didn't buy the item yourself you can only claim from the manufacturer. This has basis in common law and therefor you might have to go through the small claims court to be heard.
First stop on this route would be the Citizen Advice Bureau.
Second thing to do is compile a list of all the things you need for your case:
A list of rights you have as a customer, through statute, warranty, or contractual obligations in the particular case.
A description of the item, this includes all adverts you saw before buying the goods, descriptions by the vendor on their website etc.
details of the problem
how long you have had the goods. Or, if you have not had the goods at all, when you were supposed to have received them
when you first noticed the problem
details of what you have done about the problem, if anything
if you have already spoken to the trader about the problem, details of what was said
copies of any documents, for example, an order form, credit agreement, price quotation, instructions, an advertisement or a guarantee
how much you paid, and any receipts or other proof of purchase.
Then contact the vendor, and ask to speak to the owner/manager, dont waste time on the customer services people.