"Has anyone got any advice or had any experience with trying to make a claim through a warranty of this type?"
It's difficult to answer your question because you, apparently, aren't able to tell us what it DOES covers - only what is DOESN'T cover.
No one will cover you for virus damage - that's what anti-virus programs and common sense are for.
However, if the warranty covers accidental damage to the PC, that it might be worthwhile.
A couple of years ago I bought a new Dell laptop for my daughter to take to University. I also bought Dell's 3-year accidental damage warranty.
A few months after starting University, a heavy metal photo frame fell from a shelf onto the laptop keyboard - rendering the keyboard useless.
A quick 'phone call to Dell and 24 hours later an engineer turned up at my daughter's Hall of Residence and fitted a brand new keyboard. Problem solved.
So, to answer your question, I would swear by accidental damage warranties!
You pays yours money and takes your choice.