I would like to change my first name. How would I go about it, and how much would it cost?
You can ask people to call you by whatever first name you prefer in everyday life: indeed you can alter your surname just as easily as long as you are an adult and your motive isn’t fraudulent. However its possible your bank, and almost certainly institutions like the Department for Work and Pensions, will require something more formal. A solicitor would probably charge you around £75 plus VAT for preparing a change of name deed. There are special provisions relating to the change of a minors name, and, technically, forenames given at baptism can only be changed by Act of Parliament or Royal licence!