Mitsubishi Colt Engine Problems
Mitsubishi Colt engine light problem
You've got no recourse to the dealer or to Mitsubishi, the car is seven years old, and the problem you've got is fixable and shouldn't be expensive. The most likely cause is a failed sensor or a wiring issue, it is most unlikely an issue with the transmission of the main ECU.
E10 fuel in a Mitsubishi Colt
Mitsubishi's recommendation is for fuel-injected models only, so I would not use E10 in your wife's car. It would be best in your circumstances to go to the higher octane petrol.