Can anyone tell me Where is the Exhaust Gas Temperature Circuit Bank 1 Sensor 3 is please? 

Showing code P242A

And where is the best place to purchase a new one please? 

Had the same fault code with my mates car same year and model and we found it was the sensor that was in the exhaust pipe just before the flexi pipe on the front exhaust pipe, we found that there were 3 of them in total and we just unplugged each one at a time to see what happened we had different codes from the others  but the same from this one I think it was around £50 to buy, might be worth trying first 

Thank you very much 

Is it this one in pic?