I use ‘Proprietor’. It’s still a business, regardless of whether I’ve registered with CH, I employ people and I carry out contracts etc.
I know someone who claims to be the Director of his ST business – I chuckle a little every time I see it written. I was even in business with him for a short period and told him it was nonsense, but he wouldn’t listen.
I also used to work alongside someone who, as a Sole Trader, insisted on having a Bank Account that he would draw ‘wages’ from, believing that’s what he would be taxed on. He wouldn’t listen to me when I told him otherwise – i.e. you are the ‘Business’. A year or so later he finally conceded, when his accountant told him the same as I’d been telling him