I have 3 lavender plants in my yard (two french and one english) They have grown large over the years and they also grow like weeds - you can cut them way back and they will respond with growth. I love the smell, and since I have such an abundance I have made sachets for myself, and to give away as gifts.
cut the blooms when they are nicely purple and full. Cut either early in the morning or before sunset. The point being to cut in the cool of the day so that you and the bees don't have to enter into a discussions as to ownership.