The ticket vendor isn't obliged you to refund you because of your inability to attend the concert. If they've agreed to do so, it's purely a goodwill gesture; I can't see PayPal backing your claim when (in strictly legal terms) you've not got a valid claim anyway.
So, unless the vendor holds good to their promise to refund your payment, I reckon that you've lost you money. (Sorry!).
For the record though, PayPal's customer support number is 0800 358 9448.