this shouldnt affect your application in any way shape or form!! most middle eastern airlines are quite strict on medical check ups and htings like that but i believe that is because of how medical insurance works out in the middle east (correct me if i'm wrong anyone) however, in the UK it works differently as you know. even if your astma was still about and you were prescribed inhalers and ventolin etc for it, then im still confident you could become cabin crew with BA. so the fact that your astma is pretty much non existent, i dont think you'll have any problem!!
