Health Insurance query

Hi,

Mods feel free to move if this is in incorrect forum.

Ive had health insurance for quite a while now but I feel a bit ignorant regarding what it gives access to etc

I have a specific query regarding treatment options for Chronic Lymphocytic Leukaemia (CLL)

If you are insured can you get access to drugs like ibrutinib etc?

is there a list somewhere that insurers will cover for all illnesses etc.....like an approved list or something, if its on the list does that mean a public patient can get it too just that they may be waiting for consultation etc....or is it down to the insurer

If the drug/treatment is on that list does that mean an insured patient can get access to this treatment if consultant etc recommends it?

Appreciate any help or being pointed in the right direction