Glad you sorted it and good that you're going to get it in writing. For others with similar queries this post might help: //www.diynot.com/forums/viewtopic.php?p=1640788#1640788
There's a good summary of the law on outbuildings and the legal shed height here.
The government planning portal has the definative answer on what they term as outbuildings but not always in everyday terms, and remember the local council planning officers are at the end of the phone for...