With the regulations constantly changing, you may not need planning permission to extend your home or erect an outbuilding - ask your Local Planning Authority whether you do.  Bear in mind though, that even if you don't need planning drawings, and you opt to contract Building Control under a Building Regulations Notice, if you don't have some form of drawing for your build, it is very unlikely that you will have a smooth journey.  Even if you do everything yourself, with no plans, you are planning to fail.

So to the planning submission - referencing a non-listed building.  This needs to be scaled drawings (1:50 or 1:100) of the floor plans, elevations, cross section and roof along with site and location drawings, foul drainage statement, and a planning statement explaining what you intend to do and why so the Parish Council and Planning Authority can more easily understand the whys and wherefores of what you want to do.  You may also have to submit surveys such as bat, land contamination, topographic, ecological, mining....

The Planning Portal contains useful information https://www.planningportal.co.uk/planning and your Local Planning Authority will have a list of their required documentation for different planning application types.

Once you submit your application and pay the fee, a member of the LPA carries out a verification of  your submission and lets you know if anything is missing, but if all is OK, you will receive a letter (probably by email) saying your application is verified and detailing when you should receive their approval or rejection of the application - should be eight weeks from the verification date.

All LPA have the remit to consider planning applications favourably and should work proactively with the applicant so that a mutually agreeable solution is achieved.  If things are taking a little longer than usual, the LPA should request your permission for an extension.  Your response is your choice.