I thought it would help to hear a not very smooth path towards c25k.
I am 47, started fairly unfit, mildly asthmatic and slightly overweight. I started in September and am now at the end of week 6, did my first 25 minutes run today. You may have worked out this has not been a 6-week plan.
By week 3 I was struggling so I repeated it. I then developed a really bad hip, virtually unable to walk, so I took a week off (went for a swim) and did week 3 again and it was by then fine. Weeks 4-6 I have done each run twice. I have had to up my asthma medication to allow me to breath in the cold.
Sometimes it feels like I'm exhausted and sometimes it's fine. today was a great success, but I might do the same run on Monday and be half dead.
Overall it's been brilliant and I would recommend it to anyone. If like me you are likely to struggle, it's helpful to see the process as being the goal, rather than 30 minutes of running.