Looking for insurance that covers out of network practicioners

Hi everyone, I live in the UK, I am looking for (Worldwide or UK based) health insurance that covers out of network practitioners and potentially naturopathic health/functional medicine as well. I've been severely unwell for 3 years now to the point to the point where it has completely disabled my life. The GP is not helping and its going to take investigation to see what's going on. I've been living in a moldy home for a while and I think that's why my health has been so terrible. Issue is that normal dr's don't treat mold toxicity so I would need to potentially find a doctor who does functional medicine as well. I cannot afford paying for these Dr's with my own money at the moment. Any tips would be great!