I don't sell many records, but i've had a similar problems of a record arriving broken to a customer in Germany, one posted the same day to Portugal took longer to arrive but was intact. I used the same packing in both parcels & sent all the details they required, proof of purchase etc. photo's from the customer of the packing & broken record & heard nothing. I phones them on several occasions for an update only to be told "I'll look into it for you" The final time about 3 months later the P.O. guy I spoke to said "I think you've waited long enough" and I got a refund within a few days. I think they deliberately do nothing & hope you give up, I had to pester virtually weekly at the end to get a result, don't give up that's what they are hoping for. I no longer send abroad, as I don't think the risk is worth all the hassle if there are problems .
Good Luck