RRS suspension strut lifespan
Two examples for non-Genuine (delphi OEM or Allmakes):
Island 4x4 has fronts for 133-166 gbp (Front - Island 4x4 - Specialists in Land Rover and Range Rover Parts and accessories for all models. UK and worldwide mail order.) and has rears for 175gbp (Rear - Island 4x4 - Specialists in Land Rover and Range Rover Parts and accessories for all models. UK and worldwide mail order.).
Lrdirect has a few other options at the high end of that price range. I reckon freight would be in the order of 175GBP so buying Delphis from Island would probably set you back about aud$16-1700 incl freight (possibly a little more /less depending on freight choices and skills at avoiding the import duties and exchange rate etc).
The genuine ones seem to be about twice the price and you'd have to form your own judgement about the pros and cons of oem / genuine / used. Anyway good luck !