Well, the deed is done. I found a 2004 LC4 120-series with 103K miles for £6300 somewhere close enough to view. Externally it's in very good condition, with fewer marks than the 2013 Berlingo I sold last week.
Internally it's not bad, though of course the driver seat bolster on the right-hand side is a bit tatty. It still has the toolkit and jack. The seller is a pleasant and steady retired gent who has owned it for 10 years; he is the second owner. He and his wife need something a bit smaller now that they are no longer doing the miles. He had all the service history, original handbooks and other documentation.
I took it for a test drive and it seemed fine, no strange noises or unexpected movements. It was audibly a diesel but not too noisy. So I bought it and piloted it home 60 miles. It's comfortable and drives well; large but not unmanageably so. Because it seems to use a lot of the same switchgear as my wife's Toyota it all seems familiar. (As I was on a tight schedule I had to eat on the run and found that one advantage of an automatic is that if you're careful you can eat a sandwich with one hand while driving.) Predictably it hardly noticed our rough track.
The front window on the driver side clonks a bit and a couple of the doors are stiff, so I will have our local independent garage take a look at it. No doubt there will be things that need doing, but overall it seems to be a pretty straight car at a good price.
Now I need to sort out a double din head unit with a touchscreen and other goodies!
Thanks to everybody for their input in this thread.
Dan