Even the cheap ones should be fit for purpose. But in the real world, not necessarily.
Have a Google and find your local motor factors. These are the places garages use to get their parts. Find out prices of the sensor in NGK and/or BOSCH.
75+ vat seems very cheap to me.
If theyre asking that for it, the chances are the garage is fitting crap to your car.
I had the very same sensor fitted to my car a couple of weeks ago. Was a genuine part from SEAT. cost me ÂŁ175+vat. Ive still got my fingers crossed that my light doesn't come back on again lol. The one removed from my car was (believed to be) the cars original and my car has done 121k now.
It could easily be a fault with something else but its worth being 100% happy and confident in the sensor thats fitted so if it doesn't fix the fault, you can confidently move on and check other things.
Also, ive heard that bosch arnt the best anymore as production has moved to China and the quality had dropped. Maybe true, maybe not.