Here is my list of selected plants that will bloom in an English Garden in July.
Alchemilla mollis or Lady’s Mantle
Astrantia major
Campanulas
or Nepeta
Cotton Lavender
Common Marigolds
Cornflowers 
Delphiniums 
Foxgloves
Feverfew
Hardy Geraniums
Heucheras
Honeysuckles
Hydrangea macrophylla
Lavender
Lavatera or Mallows like a sunny spot and have lovely large flowers.
Loosestrife- Yellow flowers that is easy to grow in a damp spot in either sun or shade
Lupinus
Monkshood or Aconitum napellus have flowers similar to Delphiniums . can grow to 5 ft (150 cm).Prefer a spot in moist soil with light shade
Rock rose or Cistus,has single rose-like flowers which start flowering in May and go on flowering for about 3 months. They like a sunny spot and tolerate quite dry soil.
Roses – bush and climbers as well as patio roses
Sweet Williams Yarrow
Sweet peas - No English Garden is complete without these beauties!
If you need more info on perennials then check out the Royal Horticultural Society's book of Perennials. I have this book and it is a wonderful refernce guide - full of hints and tips on planting and over 5000 plants described! a book to dip into in the winter months when you are planning changes in your English Garden.
An Encyclopedia of Perennials
Enjoy your English Garden!
