Thanks Kaz,
I drove the car today to see exactly how it reacted to different braking input.
Driving from cold and applying a small amount of braking force, triggered the chirping and the pedal to feel as if the ABS had been triggered when it had not; so kick-back and the feeling of the pedal falling through its travel.
At low to medium speeds the chirping would kick in regularly when not using the brakes.
At higher speeds with higher braking force, the brakes worked fine, but would chirp and kick when I backed off the brakes but was still applying some pressure.
Overall the kick was quite strong, but most disconcerting was the clunk as the pedal would fall through it’s travel as though I had lost traction.
The picture is the invoice for the seals replaced at the time of the rebuild.
Apparently when everything had been rebuilt/replaced, the previous owner reported that the ABS was improved, but still displayed the above characteristics at times.