England UK

I have had motor insurance with Marks & Spencer for several years with
no claim.
Now I have just had to put in a claim for slight damage done when the
car was parked and nobody in it. The third party kindly left their
name, address and insurance company on a note apologising for the
damage.
This was all forwarded to Marks & Spencer who gave me instructions on
proceedures to get the car fixed.
Out of the blue, came a recorded delivery aggresive letter from Marks &
Spencer cancelling my insurance demanding the cover note and policy
back.
Anyone else out there had this done to them.
This now means I have been blacklisted, when another insurance company
asks if I have been refused insurance, I have to say yes.
All this for one claim where the third party has admitted liability and
all details have been given to Marks and Spencer. I have not claimed
from Marks & Spencer before.
I went to Marks because I thought I would get a decent service, I was
not after cheap insurance.
I have telephoned them but talking to a brick wall is easier.

Any thoughts please.