Some good news to report (if anyone is interested) - I've submitted my doctor letter/note to the AFCO and I can now run the 1.5 mile run in 11mins 30 secs with is 41 secs under the required time (proof enough that asthma is not an issue for me)!
PS - in regards to the letter that I submitted, does anyone know what will now happen to it and roughly how long it'll take for me to get a response? I'm assuming it'll get sent to Cranwell.