depends on what you have in the consumer unit
old style rewirable fuses and the 3A fuse should blow first
newer style mcb's and the mcb will trip before the 3A fuse
that wasnt the reason for suggesting it, more because you would have to turn off the whole lighting circuit should any work be needed on the new light, which might not sound to bad but then imagine your up the ladder messing on with light and someone comes home, finds the light in the bathroom wont work and realises the trip thingys down, switches it up and....
this has recently been reported to have happened to a young plumber, he had turned off mcb under the stairs and went into loft to do some wiring work only for the old lady in the house to turn the mcb back on..... killing him