(uk) been a self-employed plasterer for 5 years and have 2 job interviews today. what should I be asking?

I've been self employed for 7 years, 5 of those years I've been plastering and can plaster to a standard that ive been told is pretty high. It's been so long since I've been on paye that I have no idea what questions I should be asking to make sure I don't put myself into a position where I work for a company I hate. What should I be looking out for in a good/bad company?