Larry, Gareth. Thanks for your help. I bought the genuine part from Audi for £83 as I’m still in PCP with them. An Audi technician then showed me the wrong location for the sensor, indicating it was behind the brake pedal under the dash. Spent an hour removing various bits of plastic and upending myself to no avail, I then took to you tube prior to your message coming through Larry. Found the sensor and replaced it in about 3 minutes as you said. That didn’t clear the stop/start fault which happened at the same time, but I found another you tube clip in which a guy said to remove the wire connected to the side of the battery, reconnect it and that should reset the fault….and of course it did. I dread to think how much Audi would have charged me for that little lot, and I am somewhat flummoxed as to why the technician showed me the wrong area of the car to find the sensor.
Regardless, thank you so much for your assistance and advice. Happy driving!!!