Ford Ka power steering fault?

I have an X reg ka, the power steering bottle where the pipes go into have alot of seepage (which got advised on its MOT) well it has a slow power steering leak takes approx 3 to 4 week to run empty, i was told it can't be the steering rack because there's no black fluid out of the rack gaitor so it has to be on the low preasure side.

Also after starting the car and turn the steering wheel it goes heavy then light and it does the same when driving at odd times.

Has anyone come across anything like this before?

Hi the pump itself may have a leaky bearing which with such a small loss could be why you see no signs of where it is coming out.
now we come to the real answer is it really worth doing anything about such a small leak. Given the cars age.

Heavy then light is often sign do air in system of pump / pressure relief valve issue.
Since it can't eat power steering fluid.it must be leaking it. We need to check where from.eg around pump itself? Pipes and joints? Rack gaiters?
Do we have any fluid on floor after parking overnight? Clean all areas we suspect and then use tissue paper such as kitchen roll to dab around all joints etc. When we get a wet spot! We may have found our leak pointy.