I couldn't get the links to work either.

Try this for Amex companion ticket terms and conditions and this for standard redemption rules.

However, it only says "A fee as specified online at ba.com will be charged if flight bookings for Award travel are cancelled by the Member prior to departure. Provided a cancellation is made more than 24 hours prior to the scheduled departure of the first flight in the Award itinerary the Mileage charged for the Award will be re-credited to the Member's account."

Not very helpful. I think from memory the cost of a CE cancellation was £30 and you get the miles/241 back.