Postscript

So, though in retrospect I'd been having a bit of trouble with it for a while, the exercise-induced asthma only kicked in in January, first as what seemed a symptom of a heavy (bronchial) cold but it wouldn't go away subsequently, until I saw a doctor and got the steroid inhaler. However, I have just read something that made my jaw drop - wait a minute! That was the big change I made exactly at the new year - I cut caffeine out totally, from having been a 3+ cups of coffee a day person. Hmmm, must raise this with doctor on the phone next week....