On thing I found, Neil, was that I simply didnt have enough time in my lunch hour for the runs I wanted to do. It was OK for a quickie, but steady longer runs just hurried me.
I found by switching to either evenings or before work were better, as I was able to give myself time to sort myself out.
There are considerable disadvantages. It takes a lot mentally to get up even eralier that I do on a standard work day (currently 6.15 am). And its even harder after a days work and having of course to run in the dark this time of year. But it does give me the opportunity to run for a little longer without the pressure of having to get back to work/ start work.
Incidently, you are quite capable of doing a 10k now. Just take your first one easy, dont go blasting off, and you will find you will cover the distance.When picking a 10k race, I always look at previous years results to check Im not entering a race beyond my capability (as I am a slower runner). You will probably surprise yourself. Good luck!!