Well, as I suspected, my ipod - based Nike+ has been wildly inaccurate. It has been massively over-estimating my distances and therefore also under-estimating my pace. My lovely new Garmin watch confirmed these sad facts.
So..... although I can clearly run for nearly an hour, my 5k time is still over 30 mins and my Nike+ '10k' was likely to have been more of an 8-9k 😢
It's very disappointing but at least I now know where I stand/run.
In addition, it's not as bad as my partner's fitbit app which insists that he has been running across water in the harbour 😂 Definitely not part of the C25k plan!