I walk the dog in the dark (with a head torch, obviously!!) so will continue to run in the dark during winter... I need to be at home before my daughter wakes up at 7.30am so can't postpone my runs. I live very rurally though, so don't feel unsafe.
Went through Strava and looked at my old runs, I have gone from 9 minute km pace to 7 minute km pace over the last 7 weeks, without focusing on speed at all (although I have done the 1 minute sprint at Jo Whileys urging if I feel I've got it in the tank!) So I think as long as you run at a comfortable speed, your body will automatically speed you up as you get fitter etc.
I plan to use Strava to sometimes record run only (rather than run + warm up/down) over the next couple of weeks, but I think if the app can jump me from 25 minutes to 28 minutes between weeks 7&8, the jump from 30 minutes to 33-ish shouldn't be too big for a 5k!! Obviously if I feel sore or struggle, I won't push myself.
Does anyone else use Strava to record runs?? If so, and you fancy a bit of a mutual support club on there (kudos all round etc) message me and I'll add you as a friend on there!!