Planning Rules vary enormously depending on location, local planning issues, restrictions, covenanats and existing buildings.
Generally we assume that you will have to apply for planning permission!
There are ways around this, our view is to hit this probelm on the nose, well sort of!
Our experience is that most councils are pretty receptive to the Blueriver approach. Plans are quickly created that allow a strcutured discussion, take along a few pictures of ones built previously and a colour chart and hopefully they will give you the OK prior to submission of formal planning regulations.
The colours can be tailored to blend in with surrounding buildings and/or countryside.
The height and dimensions can be easily adjusted to accomodate local planning dos and do nots.
The building can be structured from very 'slabby' through to almost Gothic with lean to structures and sub sections.