Thanks to this forum I got some good advice when my lower calves caused me some real problems at the very end of the w6 r3. So I didn't run for 4 days (twitch, twitch) to let them properly recover and repeated w6 r2 yesterday evening.
This time, as advised by the good folk on here, I drank a glass of water about half an hour before I went out, didn't do any stretching beforehand (apparently likely to do more harm than good as I was doing this before Laura's brisk warm up walk!), but stretched carefully and thoroughly at the end. I also armed myself with ibruprofen and arnica gel for afterwards.
So this is the day after the run - and my legs feel great - none of the soreness/having to walk like I've wet myself/blanching at the thought of coming down stairs like last time - just that lovely gentle 'i've been doing exercise' ache.
I'm so relieved - couldn't bear the idea of having to stop running for a couple of weeks (that alone shows how far I've come!!). Thanks for the help