Steering wheel judder at any speed might be pump-related

[Tentpole]

Fiesta 1.4 16V Manual Climate 06

The steering wheel has recently started to judder/vibrate, not really bad and it's perfectly driveable but disconcerting. This is noticeable when stationary or moving at any speed and even with slight steering wheel touches, not just full lock. It happened immediately after I had the clutch replaced during which the clutch slave cylinder was also replaced. I mentioned this to the mechanic but he said the clutch/brake system is separate from the steering hydraulics so should not affect it. Also this is a climate model which has a separate steering pump drive belt and pulley which is independent of the main alternator belt - so said the Haynes manual but I checked just in case, and it seems to be so. I checked fluid level which was just below minimum and it only took a tiny bit of fluid to top up. There is no tensioner to adjust as far as I can tell.

Is this imminent pump failure, slipping belt, air in the system or what? We are about to give it to our daughter for the cost of getting it fixed up so before I take it to be looked at, any ideas please, people?

[DieselPig]

Sounds like air in the system. Start the car and move the steering wheel from lock to lock. Check the fluid level whilst doing so.