I cancelled insurance for my 2 (both under 5), and instead set up a standing order for 100 per month into a separate current account so there's money if I ever need it for medical expenses. With free GP, and public hospitals, I'm comfortable that I didn't need extra cover that I couldn't afford to pay for if needed.
Saying that, I've friends who have needed treatments for their kids and used the private system to get seen quickly, that they couldn't have afforded without insurance.