I so envy you! I love lavender but one has to be careful planting it here as my understanding is that it hates wet feet. Some people have said it does best planted in a rock wall.
I've been thinking about gravel paths; there was an article by the gardener in our local free newspaper. She said to dig down 5 to 6 inches and she didn't mention a base. What do you call gravel in the U.K.? Gravel here in Maine is glacial till, very small, whereas in Ohio gravel was crushed rock, about an inch big.