'Best' depends on whether you want a cheaper upgrade or a more certain upgrade.
Options are in somewhat order of price:
Hope for an op-up from WT to CW (very unlikely)
POUG/AUP to WT+ and hope for an op-up to CW (unlikely)
AUP from WT to CW (unlikely at LHR)
POUG to WT+ and AUP to CW (possible)
Fare rules upgrade to WT+ and UuA to CW (possible if CW award availability opens)
Fare rules upgrade to WT+ and POUG/AUP to CW (possible)
Fare rules upgrade to CW (certain)
Thanks this is probably the most useful answer.
I'm actually quite surprised, my flight is in 5 days and it's still showing 9's across the board. Must be very empty.
However, unfortunately, still no sign of a POUG in MMB.