I considered Montessori education but not in depth as it wasn't really an option locally.

I think that the qualification/experience/dedication of the teachers/educators matter more than the specific concept and you should really visit the kindergarten/school during a normal day. My wife sat in class of local schools during her teacher training and recommended specific schools and teachers (and that does matter: the parallel class of my oldest has a teacher with a boy-prejudice). But even as a non-teacher you should be able to at least have a look and chat.

The Montessori teaching material is very good though and that is obviously independent of teachers.

For preschool I recommend forrest kindergarten. http://en.wikipedia.org/wiki/Forest_kindergarten (the picture is realistic) All our children visit(ed) forrest kindergarten but you have to consider that certain pre-school topics may be reduced (don't need to; our kindergarten was awarded for its curriculum and is strong e.g. in math topics). Again it depends on the institution and people.