Are you sure it was because of your English? It's news to me if they have started including the reason for not passing in their email.
People often come up with conspiracies that the assessors were out to get them in particular, unfortunately the mind desperately searches for explanations to what it can't understand and comes to any random conclusion.
Regarding your english, if the message you wrote above is anything to go by then I must say it doesn't look level 5 to me. I'd seriously focus on improving your English as well as perhaps going for some sim preparation to see where you may be going wrong and be better prepared for next time. I'm sorry it didn't work out this time.