Just wanted to give you a little bit of advice, based on my own experience.
I finished the C25K and was fully pumped and ready to carry on with my 5K in 30 minutes runs, 3x per week. Unfortunately this was not to be as I developed a really sharp pain in my right thigh. Fortunately I work for a physiotherapist and I was diagnosed with IT Band syndrome. Very painful and stopped me running for around 2 weeks to try to heal it.
It has been caused from doing the same circuitous route over the course of my C25K programme. I hadn't really thought about it - but pavements are slightly cambered to allow run-off of rainwater. This means that for the full 9 weeks of my course my right leg was hitting the pavement (at a higher camber) than my left leg, putting more strain on it. After about 10-11 weeks of this, my leg began to show the strain and I ended up limping (literally).
My advice - if you run out somewhere and then back again then you don't have a problem. But if you are running a circuit, make sure to reverse the circuit every week to make sure that your legs are receiving equal treatment.
Hope this helps someone. :o)