I was struggling to guess. I think The Levellers would be very popular with a Wychwood crowd and thought they might go for an 80's legend like Soft Cell or Human League, If they got 2 from that 3 the third headliner would be really poor. The quality of the headliners has been on a slide for a while with generally one decent one i.e Travis, Texas and 2 lesser.
Would not be surprised if they went for some one like Shed Seven, Feeder, James or Razorlight along with one from someone like Soft Cell, Human League of similar and one really small name for the Friday.
I do think The Smile got added because Massive Attack dropped and M.I.A. got moved to their Mordor slot, leaving space at Cupra.
Those were special small venues though. I wouldn't necessarily count on those showing up at PS.
Green Day
Bullet
Frank Carter and the SP
JEW
Judas Priest
Rise Against
AFI
Sleep Token
Deftones
Beartooth
Amyl and the Sniffers
Spiritbox
Skindred
Korn
Slayer/Rob Zombie
FIR
Yellowcard
I wouldn't really know placings more than that.