In reply to Donotello:
When you say fully comp have you investigated those hire car insurance companies online?
They are usually something like £20 for a week's fully comp cover compared to 10x that as you have seen.
There was a lengthy posts about people's experiences of this last summer on here, I think about Majorca or somewhere.
As many people complaining about big companies as small ones - seemed pot luck.
I went to Portugal, with a company that also had a number of 1* reviews for ripping people off with insurance etc. - but I went prepared with my credit card to put the 1,000EUR+ deposit down, and I had my insurance sorted online separately, had no problems whatsoever.
I will say I read the T&Cs meticulously and the guy in front of us got turned away for not having the right card in the right name that it was booked under online (or something like that) and after a long time arguing he stormed out furious (as you can imagine - he'd just landed and he had no car).
I think I used "Money maxim" for the car hire insurance
https://www.moneymaxim.co.uk/