Dear Jan;
        This is a very good question.  The taxonomy of a large proportion of
the northern Buccinidae is totally nightmare city, due to extreme
variability of most of the species - a variability that even extends to
protoconchs and radulae!!  The famous French malacologist Bouchet
tackled that family in te North Atlantic in the late 80s, early 90s, and
even he had to admit defeat on many species.  Koen Fraussen is actively
working with the group, and if all goes well, i hope to supply him with
some more material later in the summer - but it is a slow, laborious
process which may never be completely resolved.
        Colus togatus i think is indeed validly different from sabini - it is
quite distinctive.  Who was the source of your specimen?  Anyway, Colus
sabini is even more difficult to get, and i think it is unlikely you
will encounter it anytime soon.  I don't off-hand recall what the
differences are, but i do consider them both as valid and distinct.  I
haven't been able to reach Mr. Fraussen recently, but Guido should be
able to put you in touch - he will have  all the detailed info at his fingertips.

In the Foggy Foggy Dew,
Ross.