Are they worth it? It depends what you want to get out of them. If you're wanting to experience something out of Halloween, Scream, Nightmare on Elm Street or Texas Chainsaw Massacre, then you'll be disappointed. If you're after something more like Woman In Black - ie spooky stories with some amazing sets, actors and some jump scares, then you'll love them.
Times and queues: Book them early in the day just after they open - there'll be queues on the day you want to go, but you'll get them done all within the 2hrs allowed if you do them early enough. And there is always leeway - if the maze hosts know it's busy and people are struggling to get round them in the time allowed, they'll be relaxed about it. They are all inside so it being daylight outside won't make any difference to the experience. And doing them within the first hour of opening means you should get a full compliment of actors in each maze as it won't be time for their tea breaks!