Declined cashback after 6 months of waiting!
I went with M&S Car Insurance as they came out at a good price with good extras and with cash back made them only slightly more expensive than other companies. Waited months for cashback to come through, login today and it's been declined! I also didn't check soon enough as I'm also over the 45 day claim window so now my cashback is lost, I've only ever had this problem once before with BT who paid after making a claim.
Just goes to show, never rely on the cashback!