Update, I have now changed the hydraulic oil and replaced the and cleaned the filters. However this has had no effect on the power steering, it is still heavy, some time I am sure it is worse than other times, but always requiring high engine revs. I have also experienced the front loader locking in the down position, which I believe to be caused by a faulty quick coupler, but cannot explain why it does it, as I keep them connected, so dont know how it could lock up, but i disconnect it tap the end to release a bit of pressure, then it works again!!
I have to say, I don't like this tractor anything like my old yanmar, although it does have more power and cuts the grass well. I wish I had the manual gearbox and light power steering!