Brakes on 300tdi disco

Hi again, looking at overhaulling my 300tdi brakes. Would love a more modern feel but going to replace the pipes and O/H the calipers. Can anyone tell me is the threads for the brake fitting UNF or metric? I have some metric fitting that seem to fit but thought id seek some advice here first.

Also has anyone had a go at fitting up rated discs or pads and found much of an improvement? Again dont want to go that route if there is still little difference.