I too have asthma , mine is induced from having wet pleurisy three times and cysts on my lungs from ongoing chest infections, and idiot me tried to continue to train thru it making it worse.
I take a turbo inhaler twice a day , and do progressive lung exercises ... inhale 1/5th capacity and without exhaling take in another 1/5th and continue until you can't take in any more, hold it for 30 sec then release it the same way you took it in.
This and a Turbo Inhaler has done wonders for me.
Also take an antihistamine daily , if yours is allergy related in anyway it will help out.
Iron tablets with vit C will help with your blood/oxygen, if you are feeling latic saturation after hills [as I did] take your inhaler and walk for 3km after the ride , slowly.
Hope this helps
Is this progressive breathing something you do for a few repetitions or for a certain amount of time?
I have been using an antihistamine nasal spray called Beconase but discovered it contains the same active ingredient as the preventer inhaler so need to check with a doctor whether I can use both.
@eric; you are probably right, I could buy in cash in a few months time but then I don't get to try it out on the summer roads. I'm not sure how much I would gain from having a power meter without being able to interpret the numbers. There is no reason why I couldn't buy one in the new year though if i change my mind.