There are 39 true species of lavender
Many don't grow on our shores and couldn't survive in our climate. Some are native in Southern Europe, others in Asia, Africa and The Americas. In the UK we generally grow Angustifolias ('English Lavender') and Lavandins (Grosso and Vera are popular examples) although some Stoechas lavenders ('butterfly' or 'french' lavender) can survive too.
The species Angustifolia has hundreds of varieties, they're particularly hardy and can easily withstand very cold winters. Generally they are compact, sweetly scented plants which aside from lilacs and deep purples also have pinks, violets and whites too. Angustifolias usually flower between mid June and mid July. The oil is expensive and not only offers an excellent perfume but is a natural antisceptic and a very popular essential oil amongst aromatherapists.
Lavandins aren't a true species instead a hybrid mix of Angustifolia and Latifolia, they're the most popular plants used by lavender growers as they produce far higher yields of essential oil. They are excellent for attracting bees and also make very good bunches as their stems are much longer than other lavenders. Weather depending the early varieties will be in bloom from mid July and the last will still be in flower by the end of September.