All insurance is a gamble really. There are some advantages to private health cover which include - choice of doctor, choice of hospital, private rooms, shorter waiting lists for elective surgery etc plus some refunds for ancillary services like optical, dental etc.
If you wait before joining a private company, the premiums you will pay will increase for every year over 30 at the time you join up.
There is a search function on
iselect which could be helpful to you.