Ok, coast to a stop at traffic lights for example, and as soon as the car's speed drops to say below 5mph, the pedal kicks back and hardens as the abs kicks in. You have to keep your foot on it for the car to stop.

No light in the dashboard to indicate a fault, however, I know it works as it sometimes comes on

Sounds like the ABS "thinks" a wheel is locking up when it's going real slow. Just wanted to check the obvious before taking it to a specialist.

I have checked/cleaned the wiring in the engine bay (to the abs pump unit) so far, and no change.