Welcome to FlyerTalk, patjeff63
Can I ask you a question about your existing booking? Did you book the redemption booking through BA's Executive Club or through the Avios Travel Rewards programme?
If the former, you can upgrade your existing booking by contacting the Executive Club and ask for a change of travel class. If seats are available, the additional Avios will be debited from your account. You may also be asked to pay any difference in taxes and carrier surcharges.