I would be extremely cautious OP. Factually, you have had a policy cancelled, they have quite literally informed you of this in writing.
You will be asked "have you ever had a policy cancelled?". The only correct answer to this question is "yes".
The small print on your next policy will also state "any incorrect information may invalidate your policy, and it will be treated as though it never existed"
I think that realistically, you can choose to not mention it, however, if there is a record of the cancellation on the MIB database (you can contact them and check this) then it WILL be discovered, in which case you will have your new policy cancelled as well. All insurance companies share data, so even if the MIB don't have a record, your previous provider will, and may still share the info. This would result in you having two cancelled policies on your record within a short period of time. If that were to happen, you wouldn't be able to insure a bicycle, let alone a car.
I wouldn't risk it, if you can get a quote with the cancellation, I would go with that. It's the lesser of the two potential issues.