Huge thanks, everyone - some really kind comments, which I appreciate very much.
I did sell the old lights in the end, and I'm bound to say that someone here on TZ got a real bargain. I also added another (slightly more powerful) LED light, so I now have a three head set-up which works very well.
Of the photos in the OP, only this one was taken with the LEDs...
I have taken a few more watch shots with them, and I'm happy that they're fit for purpose in that respect. Maybe I will get to try them on a Roger Smith one day