Parkrun number 6 done today, and my event's 150th run :)
46.35, nearly back to square one :( Not sure why, brain wanted to go, body said no :(
Ended up popping to the walk-in centre after, past two weeks I've felt more breathless during the run, so wanted to rule out anything sinister. Nice doctor there said that chances are it's just having a low tolerance for vigorous exercise, which should go away as I keep going. He said if I ever felt wheezy, see my own GP for a trial of treatment for exercise induced asthma.
So for once in my life, I was glad to be told I was just unfit! 
Volunteering next week, and then a friend is getting married the week after, so might be a bit breathless again the next time I run haha!