My apologies if I'm stepping on some toes Gemma.
So long as CGC marks the package as Canadian Goods returned then there are no customs fees. If they fail to do this you may be contacted by FedEx and can offer that explanation along with proof of shipment. If you get charged duty then you can fill out the attached paperwork and submitting to the government with the same explanation.
What FedEx Priority has built into the cost is the brokerage charge. Personally I ship via FedEx ground which does not have that cost built in. I get a separate charge for usually about $20 to cover brokerage. I do not get charged duty.
Andy70/Exwhyzee/Beige - " Canada - don't bother - too expensive, slow and uninsurable.So no Canadians thanks"