A3 Emissions control system warning light

I have an A3 1.6 MPI 2006MY, which appears to have an intermittent fault with the upstream Oxygen sensor.
A diagnostic scan reports the following:-
"Linear oxygen sensor B1 S1 pump current trim circuit open P2626"
"Sporadic 008 implausable signal"
When I clear the fault code the Emission warning light goes off, but I noticed that the fault code returns but no warning light comes back on.
I assume I need a new sensor, but as these are expensive-around £150, and it is a pig to access, and is very tight, are the emissions affected,as its MOT is due shortly?
The car drives perfectly, and fuel consumption is excellent.

If you don’t replace the sensor the cat could be damaged.

The car has just passed the MOT. It is unlkely the fault will affect the CAT, although I intend to replace the suspect sensor anyway.