There is a screw on the throttle housing this is the "Base idle adjustment" the idle speed cannot go BELOW this but can be raised using the ISCV. (Make sure nut is done up properly if ever adjusting this as many have fallen out from not being tightened after and there not cheap to replace/source)

2WD you need to undo the locknut first with spanner then adjust screw as you correctly say anti clockwise will decrease revs and clockwise will increase. However this isn't your problem seen as it hasen't been adjusted and was ok, so you either have an air leak or the throttle is sticking.

When these cars run they are very reliable, however as with anything old expect age related problems from time to time.

Martin