Duncan - in my experience, after this brilliant start, you'll be negotiating with the powers that be, to lay a nice flower bed down one side of the gravel garden - "to give a bit more colour and for plants to grow up the fence" and of course, running between her plants will be an Extension.... I worked this ploy 3 times in the past, tripling my running line. Unfortunately, I don't have the luxury of unused garden space now!
Good luck!