sounds like he has taken down the ceiling rose and joined all the wires that the same colour together, this happens alot with DIY'ers, what he should have done was to identify which conductor was the "switchline" (ie becomes live when the wall switch is turned on) in most installations this is often a black wire, it should have a red sleeve on it, sometimes a bit of insulation tape or a nick in the insulation or the copper conductor maybe doubled over as this wire was in a terminal of its own. if he's joined this wire together with all the other black wires this creates a dead short between live and neutral when you switch the wall switch on, this will blow your fuse or trip MCB.the overcurrent has probably welded the switch contacts together as well.
What he needs to do is switch off the power at the distibution board (fuse board) replace the wall switch, drop the new lights off, split all the black wires and identify which was the switch line, maybe best left to an electrician but if he's brave switch the power back on and test which one of the blacks becomes live when the wall switch is operated.switch off the power again, this wire shold be connected to the brown wire on the new lights and the rest of the blacks joined together and connect to the blue wire on your new lights.
the other classic mistake is driving longer fixing screws through the fixed wiring, if possible you should always fix through existing screw holes or push a small screwdriver into new position to check what you are drilling/screwing into. if hes done this he's definatly going to need an electrician and possibly the floor up above to make repairs
sparkybloke, June 2009
