So, after rebuilding the database, clearing cache, deleting/reinstalling the game, all after a thorough strip and clean, and the game still crashing, I have tried one last thing.
I have gone into the settings, graphics options, and swapped the performance preset from 'Performance' to 'Balanced'.
So far I've played a variety of games modes (Battle Royal, Attack &Defend, Strike point, Casual Breakthrough) and I've managed a solid 90 minutes without the PS shutting down.
Hoping this is the fix, but I am still not sure why it wouldn't work in performance mode.