As luck would have it, when faced by a bloke in biking clothes at their doorstep, in the dark, the lady didn't freak out. She said it may be one of hers and would put some shoes on and go and take a look.
The cow materialised on an S bend , so I'd sat on the bike with hazards flashing for a while until the cow decided to move. A car came the other way round the bend ahead, which then caused the cow to turn back towards me. So I got off the bike and , did wavy arms and cowboy noises, until the cow moved into a gap towards a gate. The gate was locked but at least cow was off the road.
It wouldn't have been a problem if I'd been in a car because I'd have had room to carry it, but my pannier has my tent in it at the moment, so I could at best have only managed a few steaks.
Anyway, other than that, it was pleasant enough night and a good meet up location. Obviously it would help if someone had actually ridden somewhere and could regale us with tales of their trip, but you can't have everything.