Thanks folks, glad you're enjoying the thread. It makes it worthwhile writing it
I thought it time for an update with my latest efforts. I left my stook rather longer than a week (life got in the way) and the Cornish weather took a turn. We had large amounts of rainfall and generally damp days, so I was concerned the nettles might have gone mouldy instead of drying out. When I eventually got back to my stook, it looked like this:
The nettles were mostly quite dry, but there was definitely some mould. I tried breaking a stalk to see if the fibres had been very damaged and there still seemed to be plenty of fibrous material, so I decided to go ahead with the retting process anyway and see what happens. I found the sheep foot bath lying around unattended, so borrowed it for retting:
I had more time that week, so checked them every so often. The nettles seem very variable, with some skins rotting and going mushy quite quickly, and some appearing little-affected by the treatment so far! In the end, I gave them a week and then took them out to see how things were going.
This one the fibres still seem fairly attached to the skin and were peeling off in strips.
This one, the fibres seem to be about all that was left on the stem
I left the nettles leaning spread out against some hurdles for a day in the sunshine. They were fairly dry by evening, so I moved them into a barn to stop them getting rained on. I'm aiming to get them bone dry before I try to get the fibres out...