lighting loop fault

[humphworld]

I have just fitted 2 new 4 spot halogen units in the kitchen. They are working fine and the switches do what they should do. However the upstairs lights are now either not working or switching on then flickering and going off. Nothing is tripping out down at the box. Any ideas please?

 

[breezer]

loose wire

probaby in the switch, (assuming you touched it) if not its where you put the lights up

 

[Lectrician]

I fit was loop in loop out through the light, then the fault is here. A loose L or N.