DIY queries renovating properties

I'm looking at a property that needs renovating and to cut down on costs, I hope to do some of the work myself. Can anyone explain how to obtain planning permission e.g. knocking down internal non-bearing walls, etc.

Minor renovations, such as plastering, painting, electrical and plumbing works do not require a permit. However, major construction works, particularly those that may be associated with bearing loads, must be made after consultation with a civil engineer or architect, to ensure that they do not affect the static aspects of the building. Owners often do their own "study" but it is better to be on the safe side than take the risk. Exterior major repairs require a permit from the relative authority.