Since my post above all the flights in our itinerary have been cancelled, soI am going to ask for a full refund under EC261, but if this doesn’t work I will need clarification about the re-booking rules. The cancellation email, like the waiver policy, makes no mention of a deadline for firming up new dates. Just ‘when you are able’.
...the value of your ticket has been retained. You would be able to rebook your travel at a later date, when you are able to firm up your new travel plans. The new flight itinerary should be completed by 31 March 2021. Please note that a fare difference may apply if there is a change in destination or booking class.