Thanks for the quick replies. When I purchased the ticket I vaguely remember seeing somewhere that "this flight is not eligible for upgrades". I just checked availability and there is nothing in F Reward space despite the flight being F9.

Has anyone experienced F from LHR-DME? Its an 840am departure so will be breakfast service en route to Moscow. Is it worth the Avios for 3.5 hours?

FWIW I usually fly this route in WT+ but for some reason when I booked the outbound was the price:

£452 Y
£416 WT+
£472 J