Dont give up on it just yet, i have two large bays in a garden i manage, the foliage has been affected by the frost but new shoots are starting to emerge, i will wait for these to push through and then prune out the small dead parts around them, you say its not recovering, scrape the bark in various parts for signs of healthy wood, if so then you may be ok, having said that some bay trees inc hedges have completely been killed off, these i will have to cut down and they may respond with new shoots from the base albeit slow, julien