Replaced bathroom ceiling light and now permanently switched on trips switch if flicked
Well you can see how they set this up.   The old lamp goes into the back side of terminals 2 and 4, and that's it, done.   I have no idea what would possess you to mess with any other wires, in the photo it's right.  

Left to right the four terminals are 


always-hot (from supply, to other load, and to switch)
neutral (from supply, to other load) and on the other side to lamp. 
earth (from supply, to other load, to switch, and to rose)
switched-hot (from switch) and on the other side to lamp.   


Put it back and you should be fine.  

The odd little white splice simply appears to be because the black wire is too short.