Ceiling light won't switch off after a new installation
From the color of the wires I assume you are in either Australia, New Zealand or the UK if the home was built prior to 2004 which it certainly looks to be.

The red and black wires are your hot and neutral lines respectively. Since there is a big junction of three sets, I am guessing they are feeders and are always live. Your light is connected across them which is why it remains on. That being said, what is that blue wire doing by itself?

It looks like the lonely blue wire is paired with the brown wire. They look like they form whats called a switch loop. The brown wire is the feed to the switch from the red hot wires. The power is then fed back via the blue wire.

If you have a voltage tester, turn the switch on and test from the single blue wire to the black leads. If it shows power, turn the switch off and repeat the test. If you don't have power, you found the switch leg which is the blue wire. You then move the brown wire of the cable going to the lamp to that lonely blue wire on the terminal strip.

If you don't have a voltage tester, don't worry. Just move the brown lamp wire to that blue wire and turn your switch on and off. Even if its the wrong wire, nothing should blow up.

Edit: added a picture for clarity