Re:
So... damper internals. Having cleaned up the damper internals I thought that all was well - however, I noticed that Rockshox do a soft spring for the Duke (which would have been much more suitable for my daughter's weight) and I also noticed that the damper had an allen key hole in the bottom and a slot in the top - to allow for adjustable rebound. Super. I thought.
So - extremely long story short (long = number of weeks of screaming, crying, gnashing of teeth, pleading to the god of MTB [Mint Sauce - in my book], accepting defeat and acknowledging that the bike would never be finished - etc, etc): the rebound damper absolutely would not budge. I tried soaking in various solutions, progressively larger allen keys (because the hole to accept the adjuster was rounded out), stud extractor in the top and large spanner, and nothing. The bugger just would not budge.
There was absolutely nothing available on the web or local bike / suspension shops for 30mm upper Rockshox of that era (beward buying Psylo's or u-turn Dukes of circa 2005, is all I can say). Same for the u-turn spring - struggled to even find a medium (red) let alone a soft (yellow). One yellow spring in the states - for £40 + £20 postage :facepalm:
Eventually (after a few weeks) I took a wing on Amazon on some XC30 internals as they supposedly have 30mm uppers and an x-soft spring. Obviously they have different 30mm uppers (have these available on eBay if anyone needs some!)
So - back to trying to fix mine. Eventually I managed to drive the adjustable part of the rebound damper out using a stud extractor in the top (clamped in a vice), an adjustable spanner on the flange on the metal outer tube and a wooden mallet (see pic below). This done - the job became easy - I drilled out the rebound adjuster hole and used some epoxy to fit a 2.5mm allen bolt (proper size for the adjuster) in place (see pic) - then cleaned up the hole where the end stop had been fitted in the slot (by extending the slot) and drilled a new hole for that with a pin vice (lonely teenage years and too much D&D

). Lightly rubbed down the adjustment tube then lubed, replaced the o-rings and everything went back together neatly - as you can see in the pics.
I gave up on finding a soft fork and decided to fit one should I ever find it. All that lot done... (and this is the bloody short version, bear in mind!

) I could re-assemble. Rebound adjuster worked perfectly (v. happy).
Final piece of the puzzle was the u-turn adjuster (that sits outside the fork, on top of the spring and allows you to adjust between 63-110mm travel) - which was also rounded out and equally impossible to obtain and odd sized. Solution for that was to wax the bolt it sits on, wax a strip of latex glove (that I placed over the bolt) - fill the hole in the adjuster with epoxy, and place it on top of the waxed glove (essentially using the bolt as a mould) - few hours later, everything came off easily and the adjuster worked a treat!
Proper decals arrived in the post from Gil today so I'll be fitting them later - beautiful quality, as you'd expect.
So, forks saved, and nice and plush again now - thank feck for that!