1. General: "The Thatcher's Craft" is an excellent little book that was produced by the now-defunct English Rural Development Commission. History of thatching, information on thatching materials, construction techniques, etc.
2. General: The Conservation of Traditional Thatch Group website is a good place for thatch information.
4. General: (Quoted from the website): "The Thatch Advice Centre is run by Master Thatchers and thatched home owners to give you the benefit of many years of experience. Our aim is to offer people relevant, useful and up to date information so that they can make an informed decision on whatever they are doing or planning with their thatched property."
5. Technical: "Standards and Specifications of Work for the Thatching of Buildings in East Anglia" is quite useful. Probably even outside of East Anglia.
6. Technical: (Some) technical data on thatch roof construction is available at the Hiss Reet website.
7. Manufacturers: See here for a list of natural thatch purveyors.