Whether or not you need to apply for planning permission, you should think about the following before you start work.
Let your neighbours know about work you intend to carry out to your property. They are likely to be as concerned about work which might affect them as you would be about changes which might affect your enjoyment of your own property. Even if what you want to do would be lawful from a planning point of view, there is no point in upsetting neighbours if a compromise could be agreed.
Think carefully about how your property will look after the work is finished. Everybody's taste varies and different styles will suit different types of property. Nevertheless, a well-designed building or extension is likely to be much more attractive to you and to your neighbours, it is also likely to add value to your house when you sell it.
Carrying out alterations and additions to your house may make you more vulnerable to crime than you realise. Make sure your home is secure against burglary and take some precautions such as installing security locks to windows. The crime prevention officer at your local police station can provide helpful advice on ways of reducing the risk.
Light itself, and minor domestic light fittings, are not subject to planning controls. Nevertheless, if you are planning to install external lighting for security or other purposes, you should ensure that the intensity and direction of light do not disturb others.
Covenants or other restrictions in the title to your property, or conditions in the lease, may require you to get someone else's agreement before carrying out some kinds of work to your property. This may be the case even if you do not need to apply for planning permission. You can check this yourself or consult a lawyer. You may also find that some properties enjoy historic rights.
Whether or not you need to apply for planning permission, there are other consents or approvals you may need to obtain before you can start work.