This morning I went out and pulled the rear seats, underneath I found the connections for the rear wheel abs sensors.
I have 4 spares from a parted out impreza in my shed so I put the multimeter across all of them, I set the ohms to 200k and tested each one, they all read 1.1.
Next I went back out to the car and tested the first one, got a reading of 4.6, thought this was odd so tested the other side which read 1.1, my answer was staring me in the face.
I removed the faulty sensor with much
and put the 2 side by side, they were identical bar the electrical connections, out came the side cutters, wire strippers, soldering iron and heat shrink.
Job done and refitted to car, abs light went straight out, test drove it and all was good
Strange thing was I tested the faulty sensor once it was off the car and it didn't give any reading at all