A master thatcher here in the US
"I decided at the tender age of 7 that I wanted to be a thatcher. When I was 16, my school counselor gave me the names of 50 thatchers working in England, and I began looking for an apprenticeship. In England, a 5 year apprenticeship, in addition to college courses, is mandatory before a thatcher can work alone. During my apprenticeship I won my first award - for best journeyman / apprentice - for work on a roof in Essex."
A nice little FAQ
A properly thatched roof done by a real thatcher would IMHO be worthwhile addition. Going the DIY route is going to be asking for a multitude of problems. There is a reason it takes years to learn to be a thatcher.