How to declare taxes as a UK contractor working remotely for a US company

I’m a resident of the United Kingdom, and I work remotely for a US company. I have a contract, and I get paid monthly, but I choose my own hours, usually working about 20 hours a week. I provided a W8-Ben form to the company that is paying me, and so far haven’t been charged any taxes in the United States.

I receive my payments into a US transferwise account, and then transfer some into a UK bank account.

I’m unsure if I am classified as self employed or as a contractor for tax purposes. Do I need to set up a business as a sole trader (https://www.gov.uk/set-up-sole-trader) to correctly file my taxes?

Thanks for the help.