Here’s a general idea of when you should be booking the various suppliers. Obvisouly if there is someone that you particularly want the earlier you contact them the better. Don’t worry, they won’t think you’re a bridezilla
Siobhán Oliver Wedding Singer and Voice Teacher
Siobhán Oliver Wedding Singer and Voice Teacher 
Great list – I agree with the earlier the better part, from the bride’s point of view, it allows you to enjoy the build up more, it gets very hectic towards the end!