"Notchy" Power Steering

[boltonboy]

Hi
2.0HDi 2005 Multispace

So ive got a weird "notchy" feel to the steering, obviously on bends it feels like it stops power for a millisecond a few times as you hold the angle into the corner, seems to be more on right turns but still on left turn too, slower turns give greater twitches than fast bends

I would say low PAS fluid but its not !!??

Any ideas please ?
TIA