Earlier quoted context omitted.
Don't touch umbrella setups. Don't go inside IR35. Businesses either hire contractors for a liquid and expendable workforce... Or they hire high skill people who take on more liability and charge for it accordingly. Be in the second group. They don't use umbrella setups.
I found inside IR35 can be much more lucrative. It's big companies that have more money, can't hire enough perms, and just need stuff done
Also if you're inside IR35 then you're an employee for all intents and purposes but without the perks of a perm position.
Be a business, not an employee. If you look like an employee, regardless of the legal layout, you'll be remunerated like one.
Be a business. They make more money.