I was with Bell and had a couple of unfortunate experiences.
They set the policy up to automatically renew, in my case I received no paperwork for the renewal. Only found out about the renewal (and terrible price) when I called for a quote - thankfully phoned before they had processed the auto renewal & managed to get the price back somewhere reasonable.
The following year I called up a few months before renewal and requested they did not automatically renew. Month later got a letter through asking for my insurance certificate to be returned to them. Called them up and they claimed I had cancelled my insurance a month previous!
They listened back to the phone calls and admitted I had not cancelled, but offered no refund for the period I was not covered for. Took 3 letters and a further month to get that amount agreed, and the head of Admiral Group customer service eventually did contact me and refund me the value of remainder of years insurance, about £150 all in, as a goodwill gesture.
Just to really f**k me off, when policy was up and they automatically renewed and tried to take the cash again!
Strangely enough know 2 other people who've had big issues. Another friend randomly got a letter as I did, asking to return the certificate. In his case they claimed they could not determine how his policy was cancelled & he never got it reinstated, instead went elsewhere.
Other was a few years back when a good friend was stopped by police as car showing on ANPR as not insured. Admiral had taken his money, issued a certificate but somehow not registered it. That took a while to sort out & was very awkward with the police.
Won't be touching any of that group ever again, although may well be that their computer systems have changed, ruling out any of the above issues.
Learnt then that cheap wasn't always best.