Originally Posted by
DYKWIA
For F class, just do a classic reward search for F on the dates you want. If you find any (unlikely!), the you should be able to upgrade from J.
ex-UK has always been very tight with F awards. Before Covid, AMS used to be great, F awards on virtually every flight when I used to check. Not sure if it's the same now though.
I find LGW quite good for F upgrade availability at the moment.
And yes, AMS is also still good.