Premium no risk zero excess insurance fail

I rented a car from LHR for four days. The key was lost or stolen on day 3, Saturday afternoon. Four hours on the phone being repeatedly put through to a closed office before someone admitted they close in the afternoon.
Got the car picked up and returned to LHR. No sensible offer to replace - so I caught the bus back.
First I get a letter saying I am liable for the cost of a new key. This was resolved easily.
Now I have had an extra 4 days deducted from my card because they "didn't get a spare key with the car" and it took this long to get a key.
I feel like I have been robbed, and have been unable to get resolution. Can't get through to complaints - sorry "customer service".
I guess the industry is so cutthroat now they have to make money any way they can.
Be wary.