JAR formally came into force 1July 1999. The UK had been conducting the IRTs iaw the new JAR criteria for sometime prior to that date. So no 'big bang'.
Irrepective which criteria applied an approach ban would apply. Either to a point 1000ft above the airfield, or with JAR a defined point on final be it 4nm or so, or the beacon on final.
So descending to the NDB minima with a RVR below minima for the approach would not be lawful, notwithstanding the intention NOT to land.
As the airfield is required to record all approaches when RVRs are reported, the PIC runs a serious risk of being prosecuted by the CAA.
I find this story difficult to believe.......