Another one you can try that I used is via "Intasure"
I still had to leave an excess "deposit" via my Credit Card - in case of a claim the Hire Company had their excess so I would have to claim back via the Insurance Excess Policy. Did not have an incident so far though.
For the amount of trips I made it was worth the £65 quid annually for me and wife compared to the total I would have have paid ( about four times that ) to the Hire Company.
It depends on how often you intend hiring a car. For regular travellers who travel several times a year it is worth it. I have a similar one which costs £49 a year. The company you hire the car from will have an excess policy. If you damage the car in some way they will charge the excess to your credit card. You then have to reclaim that excess from your own insurance.