For those who don't know - you can buy an annual policy to cover this, and if you go via the TopCashBack site you'll get cashback on the policy. I've used icarhireinsurance this year, policy £40, cashback £8 when i bought it.
I also book my carhire, airport parking and flights (when using Jet2) via the TCB site as well as many other things. Been using it for 3 years and have had £1800 in cash or amazon/tesco vouchers back just from things i would be buying anyway.
http://www.topcashback.co.uk/ref/shampers67?source=ps2new