Hello,

I usually fly London-->Tokyo on PEX/APEX tickets and in C class a couple times a year, and the occasional trip to the US on vacation (again, with discounted tix).

I've tried to get ANA to comp me (I'm a JAL GC member) , but they sent me an email saying:

Regarding our Elite Member Services, it can be offered only when the member attains the required Platinum points or boarding frequency.

We regret that we are unable to offer you our Elite Member Services equivalent to Japan Airlines Global Club as a special handling.

I might be relocating to Canada from late summer for half a year so I'll probably be doing London to Canada a few times as well (on a discount ticket).

Would anyone know the most suitable *A FFP would be most advantageous for me to join (ie. flying on mainly discounted economy tickets) AND which is likely to comp me to *G?

Thanks v. much for your time in reading this!

If you tend to fly NH to Japan and UA/US/BD transatlantic, it would be worth your while looking into BD: the elite levels are not too onerous (16K and 38K) - you are UK based, so you could earn miles on the BD Mastercard - ANA fares normally earn full mileage on BD (and double mileage in C) and redemption is very good with the miles+cash option.
Not sure about comping with JAL. BD are not averse to comping, but they would probably not regard JAL as a competitor and would not necessarily feel incline to comp (you can always ask them, though)

For comping, your best bet tends to be North American airlines. Among them, AC would be the one to go if you want an easy path the elite qualification and UA would be the one to go for more substantial/usable benefits since you do not seem to fly much to Canada. US Airways is also a possibility, although it depends on how long you think they will survive.