Hertz Car Rental - Exeter - England - UK

I rented a van from Hertz Exeter via Nationwide hire. The van was delivered the afternoon before and collected three days after my hire had finished. No problems with the vehicle or the hire itself, although leaving a van uncollected for three days wasn't perhaps ideal.
However, the main isuue for me is that I left a very expensive pair of Mau Jim sunglasses in the van, I was unable to collect them as my father was rushed to hospital critically ill 350 miles away and I had to visit him and by the time I returned the van was gone.
I spoke to both Nationwide and Hertz and filled in the necessary forms on line, to date I have had no response. It's quite clear to me the driver or the vehicle cleaner is now waltzing around with my sunglasses...to compound this annoyance, they were a gift from my father. I am and have been a Hertz Gold car holder for a number of years, renting their vehicles on my vacations and business trips around the world. Very disappointing.