This is the final level, you're back in your 'normal time'. First, grab the crystals here on the top level. Now go down to level 2 around the outer ring. Tag the 3 consoles around the edge to start the self destruct sequence. Then keep going down and go in when you hit the bottom. On the other side you'll see the hangar doors, go through.
Run all the way around to the airlock, and go outside. You can't survive forever out there so shoot carefully. Shoot down the 'timesplitter' ships. You're actively harmed the entire time outside so shoot them on each pass. When they're all dead, Now go back in.
Note from Adrian Brunton: You have made a slight mistake with timesplitters 2 on the last level when you shoot the enemy ships. You said when you shoot the ships, you'd always get hurt, but there is a corridor if you go straight out of the airlock, you'd come to a dead-end. To the left right at the end are two environmental suits. Put one on and you won't be hurt outside.
Head into the ring's center and take the elevator down to Hangar Level 5. The ship is right there - hop in and escape. Of course everything blows up when you leave, can no game end without the entire area being demolished??
The credits say:
no monkeys were harmed
timesplitters will return
On Easy level, when you win:
new arcade level - streets
cardboard characters - cheat
Note that you can't unlock new features if you play with a cheat enabled. The cardboard characters are cute though!