Provided that you are not intending to deceive or defraud anybody you can change your name to whatever you like. If you have children you may want to change their surnames so that the family all has the same surname.
Following marriage or a civil partnership your marriage and civil partnership certificate will be sufficient evidence to change your surname. Likewise if you want to revert to your maiden name, your Decree Absolute of divorce or Final Order on a dissolution will usually be sufficient evidence.
In all other circumstances you will need a change of name deed to formally record the change. To draft the change of name deed you will need to provide evidence of your current name and address, along with details of your new name.