I'd categorise them pretty much the same for everywhere bar upland
areas and the far SW: Here's how I'd rate cold/snowy snaps I remember
using your scale:

9 or 10- never seen one
8- January 1987
7- January and February 1985, February 1991, December 1996-January 1997
6- 19-23 December 1995
5- February 1994 (twice, 14-16th and 22-24th), late January 1996

There have been other cold snaps just as notable but which don't fit
that categorisation well, usually because the wind was the wrong
direction, there was not enough snow, the snow didn't lie for enough
days etc. For example the last week of December 1995 was nearly as cold
as January 1987 but had little snow (the 19-20th was the main snow
event here that month), December 1990 had one of the biggest snowfalls
I can remember yet it wasn't an easterly and only remained for 3 days;
December 2000 had a couple of very cold nights yet the cold spell was
short with only a dusting of snow.

Edmund