I don't know where you get the idea there's no compulsory NI in the UK ...! The NHS is paid for out of income tax; unless you're wealthy going in, you're going to be paying yourself and your employees sooner or later.
Technically there aren't any compulsory NI contributions below a minimum threshold (~£8k per year). Obviously you're going to hit that if you're paying employees, but for companies with multiple directors/founders - they can pay themselves minimum salary + take dividends (which don't require NI contributions to be paid).
Above that threshold means you pay an extra ~13% in employer NI contributions on top of the gross salary of your employees.
