Honestly, I would talk to your dr again. My dr didn't want to test my son at first (this was for the sweat test). My cousin was diagnosed with it and it was a shock to our family, we had no idea any of us may carry the CF genes. The dr also said that my son didn't show symptoms, so he didn't think it was necessary. I told him I didn't care if it was necessary, I needed to know for certain for my own peace of mind. I said I would pay for the test if insurance didn't. He knew that I was serious, and he then ordered the test. It was negative, but now I know.
Your situation is different, and I don't know how much the testing would cost, (and I don't know about your insurance system there), but if it was a tremendous cost for your family, and would allow you peace of mind, I would do it.
Those that know more about the testing may have other, more professional/expert advice than I do...I am just going by my gut feelings...knowing that I feel better by knowing for sure.