I don't know where to start. Can you speak to a planner first to see what the likelihood of getting permission is? how much does the whole process cost?
You haven't given us much to go on. To answer your questions:
1) Yes you can
2) The application fee for a new build single dwelling is about £400
Likely those answers are of no use, so expand on your original post
Tell us what you want to do so we can be more helpful
Provide a drawing. Learn how to use Google Sketchup (an easy, free 3D drawing program that can model your project and generate 2D dimensionally accurate plans)
Write the planners a letter with drawings explaining what you want to do and ask for advice. Provide justification of external visual changes, such as other buildings that have similar features. Be aware that they are not compelled to reply within a certain tie and it could be a long wait. The advice is useful for a few reasons:
They like you to go for advice first (i.e. it's politics)
They will point you to relevant policies (i.e. local housing policy is a mire, guidance is welcome)
The response will tell you about the bees in the case officers bonnet
One of my past case officers said that habitable rooms should have a view. This is not enshrined in policy, just an opinion of the officer but its something he cares about. I could design plans that met this requirement by moving rooms around, There's nothing stopping you reconfiguring rooms later, right now you're planning a scheme that is acceptable to policy. It doesn't necessarily have to be workable/ideal to live in
Consider putting some things in that solely so that you can take them out later, as this demonstrates willingness to compromise. Leave some things in that guidance objects to, but modify them. Later when they pick up on them, you can modify them again and demonstrate further compromise
Planners don't necessarily have the time to scrutinise your plans in detail, so don't plan everything to the nth degree. A bit of vagueness now will help your project later
Be prepared to argue, and present your case. Be prepared to bargain. They don't have to follow policy if you can provide justification for deviation on some points in order to meet others
Depending on your project, it will need supporting documentation like Planning, Design and Access Statements. Use your local council planning website to look up what others have submitted, particularly if it's a similar project to yours. Use the keyword search.
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It might also be worth watching the BBC2 series "the planners" - it will teach you about the process and the planners' perspectives and give you some sympathy for what they have to do and put up with, which will in turn help out with any dialogue you have to make to them