Yes you will, but I'd do it over the phone, when I have cancelled last two Avios bookings online - I've had to chase for the Avios back maybe 10 days later. Second one I did via Chat last week and they were returned during the live chat, so they do have some use !
HOWEVER - as these bookings don't have service fees, if you see regular availability - surely you can call up the Gold line and convert to regular Avios in one transaction without a fee ?