Problem brake light on piaggio zip 125?

When I switch on the ignition the brake light comes on without the levers being depressed, the bike has been fine for 3 years, and wondered if it could be one of the switches mounted on each of the levers, maybe a stuck contact???

Yes. A switch can be stuck on.
Turn on the key and disconnect one of the switches.
Plug it back in and unplug the other.
If the brake light goes out when unplugging a switch, it's probably bad.

i think you are right.