So I made it over the scary Week 5 Run 3 hurdle! I was a lot sweatier at the end than at the end of any previous run with the possible exception of W1 R1, but there was no point at which it felt impossible. I found it really helpful a couple of days ago to read the pinned post on this site about why the first part always feels hard, because that had been a problem for me up to that point.
I've now got a few days' break before my next run because of personal circumstances, so I was really keen to make sure I got to W5 R3 before that hiatus.