Ok
1. Connected PS4 direct to tv
2. Changed resolution down to 720
3. Turned off HDR mode
4. Turned off trumotion on my TV
5. Streamed the game over network to phone and over tv
6. Re-installed game, moved installation from external drive to local
7. Cleared game cache
8. Disabled surround output down to stereo TV speakers
9... Come to the conclusion that the game is at fault, or the PS4 standard is not man enough to handle the game.
10... Contacted ROCKSTAR and they tell me its my TV even though I've got a £1,700 brand new OLED. Yeah right