Good luck with your bait hives. Have you put your name on your local club's swarm-wanted list?
Last year was a bad one for getting virgin queens mated, it rained too much. Early autumn was too cold for thymol to work properly, and December was too warm for a guaranteed brood break needed for oxalic acid to be effective, so some beekeepers used Apistan or Apivar instead. Winter has gone on for too long, there still isn't natural pollen available in some parts of the country.
You won't be the only British beekeeper who has lost bees, but if you have pictures of your dead hive there are people on this forum who might be able to tell you why your bees died.
P.S. You will probably want to change your location in your profile, at the moment you're 'hopelessly lost'.