You can always test to see if the sensor is working properly. If you pull it out and heat it with a blow torch you will see a voltage across the sensor once it's up to temperture. Once it's up to temp you can pull the blowtorch away and the voltage should drop. By putting the torch back over the sensor you will see the voltage rise again. It should show ~1v with no oxygen and ~0v in atmosphere. I think I have that the right way round voltage wise 
thanks for the advice m8, not long changed the sensor and the fault codes away for now (touch wood)
still some issues tho, engine idle changes now and again as if its recieved a gulp of air if you get me.
made a video, soz for poor audio quality but if you listen around the 3, 24 and 45 second mark you will hear the difference, still think iv an air leak somewr in the inlet as its an AUM manifold (i know the ports will be smaller). hopefully get the proper manifold in tomoz.