Over two years ago, I completed W2 D1 of C25K at my local parkrun. I included the 5 minute warmup and cooldown walks - plus the workout required - all while going around the parkrun course. I did most of the rest of C25K at parkrun too - except for when I was travelling (we are retired and I have a camperbus)
So - beginner C25K'ers - get Thee down to your local parkrun!! - no need to wait until you can run 5K in 20 minutes !!!