I have had insurance4carhire for the past 5 yrs and at £39 a year it makes a lot of financial sense even for a single weeks rental.
Having said that I have never had to claim on it ! but all their literature reassures me!
(Then again ive read other literature that promised me a hotel , commercial center and beach club! )
It is my understanding that I pay the excess on any claim and then I reclaim it from insurance4carhire.
I have always had to have the excess blocked on my credit card but after 30 + rentals with different rental companys ive never had a problem regarding the excess.
David