I think Patricia deserves a bit more than just having her device repaired and returned after all that hassle.
I don't really understand why Sony needed a proof of purchase - did they think it might not have been purchased? They presumably know they flogged it to Waterstones at some point (the serial number would tell them that).
I'd feel disgruntled if it was me, and Waterstones were blithely assuming this was the end of the matter.
