starting a new business, can i just use a new name on paper to start with?

Answer 1

If you're not a Limited company and not infringing copyright (like calling yourself Arrods) then you can make up any name you want.

Answer 2

Yes you can but you must not use a company name that has already been registered or infringe copyrights.

Registering your company gives you some protections so consider it for the future.

When you choose a name make sure that you can register that name in the future and that a suitable domain name is also available.

Good luck