Answer: A quick search for books on "cottage garden" at Amazon.com will show you a long list of books about this style of gardening particualrly as it is done in England. Your local library may also have some.
In this country, we are perhaps more relaxed in our approach. The best advice I can give you is to celebrate the plants you love by cramming them into the space you have. A cottage garden was always just that, many plants grown from seed or divisions from friends or perhaps a few treasures brought from the more elgant gardens nearby. These gardens were tiny and were used for flowers and pleasure but also for fruit and herbs and occasionally vegetables, too. This gives you great freedom to plant whatever you'd like to grow. The main constraint is that the plants should be healthy and thrive where you place so them so you need to pay attention to the microenvironment and do a lot to improve your soil so the plants can flourish and give that "full" look.
To honor the "traditions" you might be sure to include a rose, a clematis, a small variety of apple or crabapple, some herbs such as parsley and chives and fennel, and perhaps some strawberries. Perennials such as foxgloves, daisies, iris, and daylilies would fit in perfectly as would any annuals at all. Use some containers, too. Flowering shrubs might include lilac and hydrangeas as well as caryopteris and perhaps some of the summer blooming pink flowered spireas. You can also add the non hardy summer plants such as dahlias and summer blooming bulbs. Just be sure to plant things that you really like and it will all look fine together.
From a design sense, be sure to make a path you can use to access the plants to tend them (step stones or mulch would look good), but plant the beds very full, using the minimum suggested spacings between the plants so they fill in the area. The plants will soften the look, so you can use straight lines or curves for your path, either one, whichever is more practical for getting around the space. That is another consideration about a cottage garden: nearly everything had either a practical reason behind it (the fence kept animals out) or a sort of "make it do" improvisational bent. Most things such as furniture and paths and trellises were made of modest materials and their design was fairly simple.
If you are looking for some actual plans to get you thinking, you might take a look at "Rodale's Illustrated Encyclopedia of Perennials" by Ellen Phillips and C.Colston Burrell ISBN 0-87596-570-9 and at "Perennials for Dummies" by Marcia Tatroe ISBN 0-7645-5030-6. Both of these books offer excellent advise on planning a garden and include plans as well as details about individual plants.
Have fun with your project!
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