Andy, one reason for low-speed ABS activation is that the front sensors have mismatched output signal levels (ie one is a good bit lower than the other at the same speed.). Have they been disturbed? Either one is not seated properly so the gap between the sensor and ring is too large, or there is muck and debris accumulated round a sensor or tooth ring causing a low signal. Or maybe one sensor is damaged or has a poor connection where it connects to the loom on the inner wing.