So you have 3 sets of 2 core and earth coming to the fitting.
You say you have identified the switch cable.
Without further information on core colours. I would have to assume we are dealing with old wiring colours (RED, BLACK, EARTH CORE/SLEEVED GREEN/YELLOW)
New Core colours would be (BROWN, BLUE, EARTH/GREEN/YELLOW)
If so
You have looped in wiring at the fitting, and require a spare/extra terminal for the live loop, as the three you have are not enough.
Old wiring colours: So we will start with the live loop, all reds are terminated to a spare terminal, this is not directly attached to the light fitting, but left safely inside the fittings enclosure.
Then you have the switch line, this could possibly be a red sleeved black or could be a red if twin cored reds are used. But if you have already identified this,this core would be terminated to the live of the fitting's terminals.
Then you should have two remaining black cores, this go to the neutral terminal.
All the earths will go to the earth terminal.
If you have brown and blue cores, the brown cores are treated as the red are and the blues are as the blacks are..
If this is unclear, post a picture of what you have?
On the diagram below the red core in terminal 2, could also be a black that is sleeved red. But the sleeve is not always present.
https://www.google.co.uk/search?q=Loope ... 9p1ThLiiuM:
