I'm going to leave the poor thing alone now, just play it until it grows old and confused and has to be retired, never more will it see me bearing down on it with a soldering iron in hand.
The action wasn't as low as I like (as low as I can possibly get it) and tweaking the truss rod, whilst improving the situation, hadn't got it perfect. I didn't want to admit defeat so I brought in some of my more invasive methods of treatment.
I used a knife sharpening stone to level out the frets, you can see from the different amounts of metal dust around each fret caused by scraping the flat stone over them that they weren't of equal height. Generally a sharpening stone is all that is needed - only really, really badly missaligned frets require the use of metalworking files.
This gets the frets level but leaves them scratched and rough, with a big flat part on the top of many of them, which can mess up the intonation a bit. So I masked up the fretboard thusly:
Then wrapped my thumb in light sandpaper and started to use the fleshysquishy bit of my thumb to re-profile the frets. I do this by rubbing my thumb along the length of the fret, smoothing the frets back to their normal shape - taking care to stop sanding before the height of the top of the fret drops below the height of the flat part put there by the sharpening stone.
After the neck was all unmasked and the fretboard oiled (to prevent the wood from getting all dried out by the masking tape) I put the guitar back together and put the new strings on. The action is crazylow now - like so
At the same time as doing the work on the neck I was elaborating on the designs on the guitar's body and headstock - I coated the designs on the body with a layer of clear varnish to prevent them getting worn off by playing. The body now looks like this:
and the headstock like this
Anyway. I'm going to wander off out for a walk now.
oh, and I removed the profile information bit because I'd prefer it if this wasn't there for all prospective employers to see on google when you type in my name. I'm not going to stop writing, nor will it make any real difference to my listing on google, but at least this way it's not blindingly obvious.