Your photo appears to show both reds from one cable in the same terminals and nothing on one side of the lamp.
I think the black is incorrectly labelled as a line conductor. I think it is neutral.
You would need to test with a multimeter to check, but if the black is N, then, with the power on, you should get mains voltage on the red and black. Take care carrying out this test.
The other pair is a twin red and this should go to the switch. Again, this can be verified by using the continuity setting on the MM (with the power off). When the switch is closed, the MM will beep. When the switch is open, the beep will stop.
If this is the case, then one of the reds from the twin red cable goes in the loop terminals in the centre of the rose along with the red from the other cable.
The other red is the switched live to one side of the lamp and the black will be the N to the lamp.
You may need to find out which red is the feed and which the switch wire, if the permanent live is tapped off from in the switch.
Don't forget to put some earth sleeving on the bare wires and park them in the E terminal.