I took a short cut (not best practice and costly in fluid - but probably good for the noobs - as there is little chance of breaking anything) - seems to work OK. Steering is now smoother.
- Drained the power steering reservoir, then topped up with Transmax Z.
- Ran it as is for around a month.
- Drained the power steering reservoir, then topped up with Transmax Z.
- Repeat the process once per month over the next 4 months.
- Then once every 6 months for good maintenance.