What is the part number on the original sensor? They are made by NTK and the part number is stamped into the stainless steel body of the sensor.
The connector shown in the picture is the correct one for GM Dat vehicles of that era.
Post a picture of your connector and sensor.
How did you determine that the sensor is faulty? Have you done an off-the-vehicle heat test on it?
Is yours a 3 cylinder or 4 cylinder S-Tech 2?
Somerville, Jasta & Metro are two of the Forums best guru's for this type of advice. If you are not mechanically minded and your current mechanic cant help then my suggestion is to find a different mechanic who will resolve the problem by proper testing and part identification.
The following link has helpful information for new members :- Helpful Guidance Using the Forum
A forum community dedicated to all UK Chevrolet owners and enthusiasts. Come join the discussion about troubleshooting, maintenance, modifications, classifieds, and more! Open to all models including the Captiva, Aveo, Spark, Kalos, and Orlando.