As I understand it, Ana is correct about having to fill in separate returns for each business if you're a sole trader - my accountant has always done this. For one thing, in 2020/21, I earned zero escorting so will in effect have a slight loss as I've still paid out for my phone and website. I wouldn't want that to be absorbed into the turnover of my civvy business.
Also, what Amy says about going public if you're a limited company! You often have to pay to access detailed accounts etc., but director's names and addresses are usually available without charge.