Done the "skid" test and yep its not working.
The bulb USED to work - it did when i bought the car!
In that case, get yourself a multimeter if you dont have one, and test the sensors as shown in the thread i linked you.
I tested my front 2 yesterday with a multi meter (longest part is gettin the wheel off!!)
Bought a new sensor today and fitted it, now my light goes off, and abs works fine.
So yeah, new bulb, then multi meter them to test the resistance, the one that is lower that 1.0khm or over 1.3khm or peaks around is broken.