I have never had this problem. I find insurance companies have little interest in my restricted licenses (although I always declare it).
I believed that they cannot charge more to insure a driver on a restricted license as this would be disability discrimination so I am surprised that they can cancel an insurance.
I tend to shop around for my car insurance and over the years since my diagnosis, I have used Admiral, MoreThan, LV, DirectLine, Halifax and probably others. All have been happy to insure me to drive.