I though that it would be interesting to leave this about a week and see what happens... (note - no submissions to G / no links that I have made to the website etc. / so Google is finding this itself - etc.)
the correct domain is now listing as no 2...
for some reason Google has tried to resolve another URL against it (probably one found against the original designtoo.com domain) giving a 404 - but now listed agains the correct domain as no 3
designtoo domain seems to have (correctly) vanished from the serps
all sounds as though exact matches are worth having