Just been to the shops in it, seems ok at the moment. The light is constantly on, and before that the power steering light was on and the city button didn't have any effect, but that went off.
Before this came on I did put the ignition on and off a few times within seconds as I was trying to sort something with my sterling alarm.
I have had similar symptoms on a Mk 2B Punto. Engine warning light and steering light came on but went off after a couple of journeys. A few weeks later just the steering light came on but again went off after a couple of journeys. Having scanned for similar problems on this site and elsewhere on the web I am at present tending towards thinking it's a dodgy connection (probably at steering ECU unit) or the vehicle speed sensor has an intermittent fault or dodgy wiring (see references to a wiring mod by dealers). The ECUs log faults in RAM first then in EEPROM if persistent. RAM would be cleared by dissing the battery. EEPROM clearance needs a diagnostic reader. Garages will readily attach their reader to it for you and advise of any logged error codes but beware of costs, ask around first. If the fault is transient or intermittent, successive 'good' cycles remove the logged faults.
This has happened to me this week! The steering light went on and the orange engine light was on too. But the next day the lights went off. I had it booked in to Fiat who were gonna charge me £42 + VAT to look at it so Im bloody glad its gone off - hope it stays off too!