Commercial Van Insurance Aviva Cancellation Fee

Hi There,
8 days ago I took our commercial van insurance with an insurance company, through Aviva, my employment situation changed and I called and mailed the company to cancel the insurance policy. which was £1450 payment for goods for hire and reward.
I was told:
"The cost of the insurance cancellation in accordance with the insurer is 20% of the annual premium if cancellation occurs within the first month of the first year of cover.
The 14 day cooling off period does not apply to commercial policies only personal lines i.e private car/ home
We look forward to receiving the certificate to enable us to finalise your cancellation"
Is this correct? all I received was a cover note with no T & C on it. Now I am being charged £290 for 8 days cover?
I am also contacting the FSA to askthe same question but any advice would be appreciated.
Many Thanks
Paul

Hi there,
Just to update this post I telephone Aviva who advised the 20% charge was not their charge but that of the agent/broker. They advised me to ask them for their complaints procedure, make a complaint and then submit the complaint to the insurance ombudsman.
I mailed the broker and asked for there complaints procedure and they replied saying that after reviewing my request, that this time they would refund the full amount less a small admin fee.
So a result all in all.