Ok,

First step, check your council website for the regulations,

THEN and i would do this, to prevent any aggrevation afterwoods, as the shed you will be building is looking to become expensive

Put in a householders enquiry form.

Once you have this back (not longer then 2 weeks) you are all cleared and can start building, and yes even 6 courses of bricks

My shed/cabin is about 4 by 6 mtrs but the most important part is the appex, this should not exceed the 4 mtrs

Well i would say success