Below is an inspirational video on an authentic English Cottage Garden, and some great books and products to build your own cottage garden below the article.
One of my favorite plants for an almost instant cottage garden is Salvia of every type. I have some bush-type ones - deep red, hot pink, and brilliant almost irridescent purple ones. I also love the tall 18" and 6" ones in deep purple/blue. They are light and airy and take almost no upkeep. They also attract hummingbirds and butterflies. The PERFECT English Cottage Garden plant that comes back every year!