Without a pic of the existing connections I can't say, but a typical UK light pendant from several years ago would have three twin and earth cables coming into it. All the earths would be connected to the same terminal, all the reds/browns connected to another terminal, two of the blue/blacks to another, and the remaining blue or black to another. It's this last wire that would be expected to be the switched live. It should have a short length of red or brown sleeving on it, but even if this is present, it has been known to slip off when the wires are disconnected.