The place where it will most likely be leaking from is behind the subframe mount - where the PAS pipes are mounted in a small bracket.
Mine had the same problem and my pump wore out when the level of fluid suddenly dropped.
Solution is to take the undertray off and jack the car up and remove the wheel to see exactly where the problem is.
On mine I removed the bracket and cut out about a 6" section on each pipe where the corrosion was (around the bracket) and replaced with some reinforced rubber oil hose with T-bolt style clamps. It's a bit messy dumping 1/2 pint of PAS fluid, but it made an easy a cheap fix = £20. A bit fiddly with the tiny amount of space to work in, but possible with some determination.! I flushed through the fluid with some dilluted fluid, and clean filled with new fluid.
The pipes that corrode are the low pressure oil cooler circuit pipes, and not the 1400psi pressure side.
To replace the entire length of pipe x2 is a few hundred with fitting..may require lowering the subframe to access the rack itself due to the zero space behind the block.
1.9 JTD M-Jet 16v 140ps.
Gas flowed head, Polished valves, Port matched manifolds, New Turbo.
JS-T primary Decat, MrZ full-bore Center Decat , Oil recirc tank, Big filter conversion.