Well, fortified by encouragement from you lovely people I set out yesterday afternoon to attempt the dreaded 20 minutes. I thought that running at all would be better than staying on the couch, so I'd see how I got on. I'm not sure I could have done a minute longer, but I managed it. It seems so unlikely that that leap is possible, but it is! Doing it with no podcast meant I had to sing a lot of songs in my head to keep me going!!! Oh, and I'm glad I'd read advice on here to keep going and not stop - I would never have started again.
Good luck to all of you who are coming up to this. You can do it!