Hi Steve, thank you for considering this, and for the feedback.
Was is TPI_2050077-7 posted on Apr 27th? I enquired about the EGR cooler with a VAG specialist I've taken the cars to for around 8 years (to get a feel for the "what if") and they said it's a 6 hour job totaling ~£900 with a new EGR valve and cooler assembly.
Cleaning is a possibility but they didn't recommend it because most of the cost is labour.
They also recommended changing the sensors for the reasons you suggested, as the overall cost is insignificant. And the quality of AdBlue can attribute to this greatly.
Definitely not on the same level as the A4 ha. It wouldn't be my luck for it to come down to the sensor.
I had the MIL come on the dash, so I've raised it with the warranty company and will see how it goes.
Given these engines can do in excess of 300k if serviced, the recirculation system is a disaster.