Remember, you're asking them to pay for damage, so they might want to see them, it depends on whether they think you're taking the michael. I couldn't claim on a third party's policy (as it was my fault
) but I discovered to my cost that my leathers weren't included in my bike policy. So I've now extended the house contents cover to include items away from the house.
As re damaged but not trashed - well, would you want to wear them again - I mean, damaged leathers aren't safe, are they? You're entitled to be put back in the position you were in before, so I don't see why you shouldn't claim for new ones. They might want to deduct an amount for wear and tear though.
Guesstimate - they're entitled to proof of loss - ie of the amount claimed. If you can't then I guess the insurer will horsetrade as long as it's reasonable.