Is there a way to concert from sole trader to a limited company? I have bigger plans than I thought 
There’s no conversion process, you just need to open a new QuickFile account. It’s very important to keep all sole trader activity completely separate from the limited company activity, hence the new QuickFile account.
Also try to avoid mixing Limited company transactions with your personal bank accounts, instead setup a dedicated limited company account with your bank and only use that. This will save you a lot of headache later when finalising your limited company accounts.