It's the same in Scotland, at least - and I would assume England as well because prison policies are separately administered but are on the whole pretty similar. Complain and you lose privileges. Bringng a case after release would be safer, but prisoners tend to be from a demographic that can't afford courts costs and most won't know about the JKR fund. I suspect many also aren't keen to voluntarily spend more time in court.
That claim by NHS Fife that the costs won't affect patient care is ridiculous. Just the £25k excess would pay for several minor operations, or employ an HCA for about half a year. Never mind the national effect of the full bill.
Hard to judge the interim figure as a proportion of the final likely bill. The court prep costs - taking statements, preparing arguments, creating the bundles - I assume would normally come.almost entirely before the trial starts. That will be skewed in this case by Fife dragging their heels in disclosure so a lot more prep being needed between parts 1 and 2. And the damages award comes entirely at the end. So the figure so far could be considerably less than half.