Mine was also Part VI, probably that very same showing.
A quick check on the BBC Genome Project suggests it was Friday the 13th March 1992. Next showings for VI were July 23rd 1994, then 28th September 1995.
They showed Jason Takes Manhattan on 15th November 1992, 7th April 1995 and 5th October 1996.
Can't find any showings for VII, oddly. I know VI and VIII the first ones I saw, probably those 1992 transmissions.
I strongly feel it was the Part VI in March '92 and Part VIII in November '92 screenings that I saw. I know it was not that long after the films had actually come out and that I saw them pretty close to each other (same calendar year).
Thank you for the information!