Ceiling light problem. When switched on there's no light yet power. and they're new spots.?

My partner bought 50 watt bulbs and fitted them onto the ceiling bracket but they should have been 20 watt without me knowing and now they've all gone out. Suspecting it maybe the fuse thats blown i changed it but still doesn't work although the actual bracket is live! Why does my mains tester show there is power yet the spots wont work? Thankyou in advance.