The quick answer
You don’t need a deed poll to be called by a preferred name. Friends, colleagues and most organisations will use it if you ask, and some banks, such as Monzo and Chase, let you set one in their app.
But a preferred name sits alongside your legal name, not instead of it. HMRC tells employers to put your first full forename on payroll, not a nickname, and your passport and bank statements carry your legal name. If you want one name everywhere, a deed poll makes your preferred name your legal name. Ours is £14.95, posted free.