Well the Tesco petrol thing has gone mental. Please remember who told you first!!
I phoned my garage and I am told that the car is ok to drive. Some people are having there power cut out whereas on mine the Malfunction Indicator Light came back on but the car runs normally. Seems I am semi lucky. Anyway I needed petrol today and stopped off at my local BP.
The garage are awiting guidance. It may not mean a new sensor but maybe resetting and the fuel dilution will do the trick. As I say its running fine.
Hey ho I'll keep you informed!