I would agree with corporate-wage-slave ,
Those who prefer to book something at the moment, you are welcome to rely on the zero change fee policy but don't forget that you are limited to a year after you purchase the ticket.

For those who are looking to fly during a UK national holiday, school holiday, or any high season, I pretty understand that you don't want to lose the great fares around but for those who are looking at off-season dates, there is no purpose booking maybe bookings at this time unless you are OK & eligible to travel if you are not able to cancel your ticket.

Also, bear in mind that border restrictions could change multiple times until then.