I posted a CD changer using Parcel force which I sold on ebay.

The buyer refused delivery and when it was returned to me it had clearly been dropped and was broken.
Firstly Parcel Force said it was my fault as packaging was not sufficient,
once I got passed that by stating the employee took my payment so they thought it was OK..

I discovered my insurance on the parcel was only for £100 when the item was worth £550
They offered me £25 which I turned down.

Any suggestions on how to either get £550 + delivery back from them, or at least the full £100 I was insured for + delivery costs
(if not costs for my time also)
Would be greatly appreciated.

Thank you very much