British native flowers, such as foxgloves and yarrow have been a staple of cottage gardens for centuries and wildflowers are being used more and more these days to complement modern varieties.
They are invaluable for our native pollinators, including the struggling bee and butterfly populations. Many of our native plants are disappearing due to loss of habitat and widespread use of herbicides on farmland. Growing wild plants in our gardens doesn't actually contribute towards their conservation in the wild, but it does help foster an understanding of their plight and puts them back on our cultural radar — and perhaps encourages us to get out and see them in the wild.
As importantly, growing them provides a valuable food source for our wildlife, which often cannot access non-native flowers (for example, if the flowers have been bred to be double, etc).
They can be simply stunning. In addition to playing an important role in our beds and borders, many are also good for planting in 'wildlife areas' of the garden, to encourage and support our native wildlife.