Originally Posted by
MPH1980
AFAIK - no - avios bookings become unchangable and uncancellable within 24 hours of the first flight.
Hence why it's better to do 2 one-ways than a return with avios unless you need to use a 2-4-1 or a GUF2/1 - because you get full control over both flights until 24 hours before each flight.
Price up the taxes on two one ways though and compare to a return.
Can be much more expensive long haul and occasionally cheaper on Reward Flight Saver.