Yachtsman,
My medical circumstances sound somewhat similar to yours.
Like you, I had quite a severe attack out of the blue one hot Summers evening a few years ago, and had to go to hospital for an hour on the nebuliser (after which i was fine).
The nurse told me that the steriod inhalers (Ventolin, Salbutamol) can actually make the attack worse if they are overused. I imagine that is why the label you get with the prescription says "2 puffs at a time".
I have a Class 2 and have been totally honest about my very occasional asthma.