Renault UK are not accepting any claims under warrenty regarding lambda sensor issues. It is also recommended that the tank be drained and filled with know good fuel! How we can tell its known good fuel I have no idea!
Renault have spoken to Bosch UK about the possiblty of cleaning the sensors. Bosch say the sensors are beyond cleaning/repairing and a new one must be fitted.
Until the contaminate is identified no-one knows what the deal is. So a small request....please be kind to your dealership as they currenlty know as much as the rest of us! And thats not a lot!