I don't think you cut lavender down that far, Stu. I don't think you should cut into the woody stems but just hang on until someone more knowledgeable answers! I'll be interested as I have just started with a couple of lavender plants this year.

you don't tend to cut into old wood. a light trim tends to be the advice I have always had from others.

Many thanks folks for your answers. I didn't plan to cut into old wood but about, say, 3 or 4 inches from the ground. Above this there are lots of little shoots!