I graduated from C25K at the beginning of November, and tried the Stepping Stones podcast the following week. Abject failure! I was nowhere near the speed required - I managed 5 minutes running alternating with five minutes walking, but that was it.
I went back to repeating Week 9 of C25K, and gradually over the last few weeks I have found that it has become easier. So today I decided to risk Stepping Stones again. The difference was marked - the first running speed seemed manageable, and I kept going for all but the last five minute run - I just started my cool down walk early instead. I found the general level of breathing etc. similar to how I was when running the final few weeks of C25K, so I am optimistic that I will be able to run for the full time after another couple of sessions.
I'm feeling the same sense of achievement that I was whilst doing C25K, so it's been a great boost to my confidence!