OneFifty - I was told pretty much the same thing back in November. However, the chap in the AFCO advised that you can be considered if you can prove that any diagnosis was suspect/incorrect. Hence why I needed to get a note from my GP explaining that my previous diagnosis is likely (he explained that there is no definitive way of testing for asthma) to be wrong.
Ou of curiosity, does anyone know definitively whether the RAF rule is applicable to the RN? I remember a few months ago that it was discussed here with no clear answer.