My Lavender care is the same as Liz. I have had the Munsteads last years and they do get leggy and woody but about then they succumb to a winter freeze.
I have also grown the dwarf Silver. It was 4 years old until last winter ,then ka-put.
Trimming to the wood is the way to go. I believe if you trim too hard it leaves the plant open to winter moisture and rot.
