The best way to understand Montessori is to see it in action. The second best way is probably to see a video of Montessori in action. This video gives a good overview of the Montessori Method and a glimpse into Montessori in the UK. The video is called Discovering Montessori with Tana Ramsay. A notable quote is when Tana Ramsay says:
Montessori is a way of life as much as it’s a way of education, and it doesn’t just start when the child is old enough to go to nursery school.