I thought I would share how I approached Wk5R3 and hope it might help other cautious runners build a bit of extra confidence before embarking on the dreaded 20min non-stop run. Before embarking on Wk5R3, I repeated R2 but added an extra 5min run at the end to bring the final run to 13min. It's a slightly slower way to get there (I also repeated some of the earlier runs before moving on), but I think that helped me feel that the leap to 20min in R3 was achieveable.
Kudos to everyone who diligently followed the app and went for it!