This isn't an option with an old Lloyds upgrade voucher. It's classed as an agency booking with the agent being Avios. In the past they have offered a 6 month extension. I am in a similar position as I used one right at the end of it's validity to book a trip to Moscow. When this was cancelled I waited the full 6 months and booked a trip to Santiago, Chile which is still scheduled to fly in August. When this is cancelled, I hope I get a further 6 months.