light sensor

I am trying to replace a Nema photocell kit unfortunately didn't take note of how cable was connected. There is a 3 core + earth cable (Red, Blue, Yellow and bare) leading from the fuse box to the sensor. The cable to the various lights controled by the sensor goes from the fuse box to the lights (i.e. the cables don't go from the sensor but from the fuse box).
Sensor requires the following connection Live (supply in), Load (supply Out) and Neutral. I don't know which colour wire should go into what point.
Can anyone help?

It is probably:
Red: Supply In
Yellow: Load
Blue: Neutral
but you can check in the consumer unit that the red goes to an MCB and the yellow goes to a floating terminal block or similar to the lights cable. There should be an isolating switch between the consumer unit and the sensor so if there isn't, you should fit one.

I take it you can see the other end of the 3c+e in the fuse box?
Switch the fuse box off before removing the cover. Take care where the meter tails enter the fuse box as these are likely still live.
Whichever colour core of the 3c+e goes directly to the supply fuse should transpose to Live in at the sensor, the connection through the fuse box to the lights transposes to the Load out and the connection to the neutral bar transposes to Neutral.