Everbody loves lavender, and Lavender "Munstead", the best for the US, is a best-seller every year with our perennials. There's all kinds of detail on growing it on the site; click here for the details.
But all you need to know is that lavender is really a desert plant--do not put it into "good garden soil", or it will simply die. Thousands of lavender plants are loved to death every year in the US, since so many gardeners plant them in rich loam, and fertilize and water them to death. Lavender is one of a good sized group of perennials that absolutely insists on quick-draining gritty soil--what most of us call bad soil--rocky, arid, desert-like conditions. I always recommend making a part of your garden your "desert"--bring in some sand, maybe some gravel, and make sure that area is in full, baking sun and has perfect drainage.