IF those lights are all that are on the kitchen lighting MCB then I wouldn't have thought it would be enough to trip the 6A MCB (you would require upwards of 1380W to trip it). Although you have 700W of halogens the LED's won't take much power.He swapped a fuse in the kitchen board to rectify a lighting issue - a 6a to a 10a as on three occasions the fuse has tripped due to me powering on all the lights (14 x 50w mains, undercabinet led, plinth leds and an led 9 metre strip around the skylight)
I hope the spark did test the earth fault loop impedance before whacking in the 10A breaker instead! Possibly a 6A 'C' type curve would have been more appropriate if it was tripping when you switch on.