I was having the same exact problem with my IDE not being able to find the BritishEnglish class. I have made the the language folder into a jar and added it the libraries the same way I did with the other JAR files. I also made the language-module under META-INF/org a jar file and added that as well.
I was able to get Language Tools to run as a standalone so I should have everything necessary and I believe I have put everything from the language tools program in my project classpath.
Sorry for being so specific but I have been trying for the past three days to get LT to work, I even tried using maven but was getting many more errors that I was having trouble figuring out the meaning of.
Thank you in advance,