Thanks to the advice on here I took run 1 nice and steady and quite enjoyed it, I finished each interval with the thought "I could have carried on there!" which was a nice little boost. I also found at the end that I'd knocked another minute off my predicted 5k time which was a surprise
I varied my route a bit this time so that more of the running was uphill (only a slight incline) and my knees are feeling a bit stiff now so my ever-helpful hubby has downloaded some knee exercises to add to my 'off day' strength training... 6 weeks ago I did zero exercise and now I'm running, doing strength training and feel better than I have for years, I love it!