Thank you for your response.
I will write to Zenith and ask them for more information although they were not very helpful on the phone.
My insurance was through Swinton who I have been with for almost a decade, so they had all my details on file. I hadn't missed a payment or made a claim or even changed employment so I am at a loss as to their sudden cancellation.
Is there a legal obligation for the insurer to show just cause for cancellation as their actions have financial consequences to me, or can an insurer just withdraw cover?