PSA - potential "free" Free XP.
In the armoury now, among the various submarine stuff, is a one time purchase of a crate that costs 50k fxp. Within it is a 21% chance of getting a tech tree sub, or a 79% chance of getting 70k fxp.
Rolled it this morning, am now 20k fxp better off. Obvious downside is if you really hate subs, theres a 21% chance of getting one.