I am sorry to disagree. The Rover service sheet stipulates a fluid change at a certain time. I cannot find the capacity of the Jatco box but it states a refill of 4 litres. Given that this box was fitted to Jaguar, Porsche I believe BMW Ford and a few others, I am surprised it was a failure.
I think we are talking about the Jatco JF506E gearbox here, it was fitted to Rovers, VW/Audi, Freelanders and some Ford/Mazda. You only find it on the Jaguar X-Type, as that's basically a Mondeo. I believe Porsche and BMW have used Jatco gearboxes, but I don't think either have never used this particular automatic 'box.
The fluid refill is 4 litres, but the capacity of the gearbox is 8 litres. You simply cannot change all of the oil, or even the filter, and in VW applications no scheduled fluid change is specified. The filter is internal, and it is impossible to change it without completely dismantling the gearbox.
These gearboxes are lovely when they are working, but unfortunately they start to die after the 60K mile mark. These problems are well known in VW, Audi and Ford Galaxy (VW Sharan) circles. They can be rebuilt, but it's expensive - if anyone is considering a used car with one of these gearboxes, all I can say is avoid... or at the very least, make sure you have a good warranty.