Dude, same thing happened to me.
IF you are very competetive and they have an issue with your lungs, you may be refered to the specialist in Peterborough who will generally tell you what you already know, in that you've not got asthma, or have ever. Went on without any more hitches and now on the front line.
The nice GP who is writing up your notes seems to be doing the right thing. Personally, I think that if you don't make a song and dance about it then there's a good chance it'll be glanced at and largely ignored.
They've seen plenty of these cases by now. If they haven't learned about the late 80s/early 90s inhaler plague then......
Either way, best of british.