Would Canterbury be considered in the Southeast part of England?
Yes.
http://www.mapquest.com/maps/map.adp?formtype=address&country=GB&addtohistory=&address=&city=canterbury&zipcode=
=)
http://www.mapquest.com/maps/map.adp?formtype=address&country=GB&addtohistory=&address=&city=canterbury&zipcode=
=)