These Pendix-related topic links should help, Jeremy...

Pendix EDrive 500
https://thorncyclesforum.co.uk/index.php?topic=15252.0

Pendix Central Electric Motor, suits many Thorn bicycles
https://thorncyclesforum.co.uk/index.php?topic=13734.msg102106#msg102106

Pros and Cons of pendix
https://thorncyclesforum.co.uk/index.php?topic=14118.0

Nomad/Bafang E Unit
https://thorncyclesforum.co.uk/index.php?topic=13560.0

E assist for Twin Raven
https://thorncyclesforum.co.uk/index.php?topic=14399.0

Sacrilege ?
https://thorncyclesforum.co.uk/index.php?topic=14718.0

Best, Dan.

I am not in a hurry to sell but on the other hand I don't see the point in asking for an unrealistic price only to drop it later. I usually reckon that half the original buying price is a good guide for any secondhand item in good condition.

It's probably a good thing you're not in a hurry, the potential buyer is going to need to be specifically looking for such a bike.  If they are, then your original price looked good value, half the new cost with light use is a bargain. As mickeg point out, if someone is looking for a bike with S&S couplings, it adds a lot of value, but it adds nothing if they don't require them. That potential buyer might be reading this now, or it might take ages for them to come along, but the fact Thorn are still selling some of these, indicates there is still some demand.
How much is it worth to someone not looking for such a bike? Impossible to say, I wouldn't consider spending much on the wrong bike, I doubt many people would spend serious money on something they didn't want, however big a bargain it was. Knocking a couple of hundred quid off, isn't going to change that.
Good luck with the sale.

Superb story/interview in today's online Guardian, here: https://www.theguardian.com/lifeandstyle/2026/feb/12/i-lived-the-life-ive-always-dreamed-of-the-man-who-cycled-around-the-world-for-four-years

...
I am not in a hurry to sell but on the other hand I don't see the point in asking for an unrealistic price only to drop it later. I usually reckon that half the original buying price is a good guide for any secondhand item in good condition.
...

Used Rohloff hubs retain good value.  So, do not put a price for the entire bike below the cost of a new Rohloff hub.

If you bought that in Dec 2017, the odds are very good that the rings were installed.
https://www.rohloff.de/en/company/news/news/flange-support-rings

My fantasy plan was to add some electric assistance to my Nomad, Mercury or Raven to help me with these Welsh Hills in my old age, but I don't see any route to that happening. So now I have the attention of people who know their bike stuff, can I ask if I am right on that? Or might I be cancelled for even suggesting such a thing? 😉

No not canceled, but I would suggest starting a fresh topic in a more appropriate board on the Forum. It would help me to avoid splitting the posts when it goes far astray from the original "Bike for Sale" topic.  A fresh topic devoted to electrification would also make it easier for future members to find that topic in a search.

Best, Dan.