I must say I've claimed for small amounts from Royal Mail in the past and they are very helpful and will often pay promptly if it is a reasonable price
I posted a Commodore 1084S monitor (the nice black version to match the CDTV) to someone who won it from me on eBay, and it arrived with a cracked casing and with impact marks on the glass screen. Luckily, I still had the high-res digital photos which I took for the item description, and the guy at the other end took digital photos of the damage. I sent both sets of photos and a print-out of the eBay item page to Royal Mail. I've never known anyone, particularly Royal Mail, to pay compensation so quickly!!! I got the full final auction price reimbursed! :-)
