Ok so I'm a bit of a wimp and didn't want to fry Ann Bryson's brain after she was so willing to let Leviathan take control of her. I stopped at nose bleeding, which has given me a variety of different locations throughout the galaxy and quite a large search grid for Leviathan's possible location.
Problem is, this is an 'end of game' save, so all of this entire region is swarming with Reapers - each system is taking multiple attempts to do a full scan as I'm having to keep diving out of the system to lose them.
Which planet is Leviathan on?