Where is the brake light switch on a fiat 500 ? (And can I fix or replace it easily as the brake lights are stuck on !)?

The brake light switch is on the passenger side of the vehicle. If you look up in the foot well you will see a white plunger switch that is operated by a metal plate. It's easier to spot if someone operates the brake repeatedly while you are looking. I have just fixed my wifes by bending the plate very slightly with a good pair of pliers, towards the switch, until it started to active the switch. It must bend away very slightly over time and cause the switch to stop being triggered. I know it's a little late but hope this help others in the future.

Take a look behind the brake pedal ( arm ) you should see a pin that goes in and out when the pedal is pushed. Take some wd40 and spay it to loosen the pin, if it won't go in/out then replace it.

Usually they're found on the brake pedal arm.