Help! Switching a ceiling fixture.

[FoofOfTheWalkingDead]

I'm switching from a bayonet fixing to a screw fixing in my son's room. I simply replaced the neutral and live wires with new ones and now the light isn't working. I've been googling furiously but no luck. I also can't see a switch wire, but the light worked 20 min ago begore I changed it.
Help! It's getting dark and our entire upstairs is off at the mains until I sort it.

You’ve wired it up the wrong way around…

I simply replaced the neutral and live wires with new ones

I assume you mean only the outer two wires which connect to the white flex and are threaded through the cord grips?

Not the fixed wires which are coming out of the ceiling? You haven't moved or disturbed those at all?

I see no reason why that wouldn't work, except if the new cable, lampholder and/or bulb are faulty. Can you put the old one back temporarily and make sure that still works?