It depends what you call shortish - I don't think you can go wrong with the old fave's like Munstead & Hidcote.
There are so many lavender varieties now & I'm a bit out of touch I'm afraid. Over the yrs though I've tried many different sizes & colours & they all seem to go the same way, ie woody & messy despite trimming etc.
With a hedge the secret is to take cuttings after a couple of years so that by about year 4, or 5 at the most, you have some good plants to replace it with.
Some nurseries may supply you with a quantity of hedging lavender a little more cheaply than the normal price of individual plants.
Hope that helps.