I have three cables (as two switches) out of celing - each cable with black, red and earth cable. I have a light fitting with live, neutral and earth. I have wired all 3 red to the live and all 3 black to the neutral - and the fuse trips. Help?

Are you in the UK? 240V? How was the old light hooked up? Sounds like 2 3way switches but without knowing where the power feed is, hard to tell what to wire. I would guess 2 black and 2 red are travelers and 1 black and 1 red is power to the light.

Hi, yes I am in the UK. The old light had the three red cables connected and then two black into one and the other black into another. Unfortunately the fitting was very old and broken - hence the need to replace.

I have three cables and a two way switch - so guess one cable on the light circuit and one each from the switches.

At 240V there is no neutral like we have at 120V in the US. So, you will need to find what wires are hot only when the switch is on. You will need to get a Volt Ohmmeter or neon tester and find the 2 that are hot, most likely 1 black and 1 red. However, they may have pigtailed a lead from your connected wires. Remember you are at 240V so be careful. When you find the 2 hot leads, turn off the power, connect those 2 wires to the light and then see what happens. 240V systems are not wired like 120V so we are at a bit of a disadvantage without seeing what wire goes where. If the previous help doesn't work, maybe you can post a picture