Bear in mind a lot of this stuff did not surface until 14 years later. Can you remember if you saw anyone staring in a shop window in 2008? I can't. This stuff is of no value IMHO.A lot of signs of stalking in this case as well: anonymous 'phone calls to Suzy at her flat and place of work, some answered by her flatmate (he reports on these in a Sunday Magazine article from 1988 which I have yet to unearth); flower bouquets delivered to the office and flat; someone staring in at her through the shop window.
In those crimes of his which are known about definitively, Cannan seems to strike opportunistically, working in the moment, striking at random almost. Moreover, it is almost infantile, the way he leaves clues strewn around the place. The Shirley Banks case was handed to police on a plate.
The Suzy Lamplugh case by contrast seems premeditated and planned i.e. not really Cannan's style. Or was he 'entertaining' himself while whiling away the hours inside?