What did/do you do for speed work? I've been doing a c210k programme for 5 weeks and a few tempo and progression runs has allowed me to increase my speed by 0.4 kph, albeit from 8 kph, but an increase nonetheless.
How many sessions per week were dedicated to speed work?
i would do 4 sessions per week
monday - slow pace 10k (below 60 minutes)
wednesday - fast pace 2.5k (below 12 minutes)
thursday - slow pace 10k (below 60 minutes)
saturday - normal pace 5k (below 25 minutes)
so only 1 day was speed work the wednesday where you would be running at a pace that by the end of the 2.5K you wouldn't be able to keep the pace up for more than a minute longer.
that was my times i aimed for and built up to then beat. you may want to add say 10% onto those times since you are a beginner maybe even 20% and then try and get them down every session by say 1% per sesion.
so overall i was doing 27.5K per week but only 2.5K was speed work. 5k was running pace what you would wanna do on the day. the 2 x 10k were to build stamina, fitness and cardiovascular health and to burn calories (get slimmer).