Well bugger me sideways, it only worked perfectly first time!
Couldn't resist, I soldered up one of those boards with the 2.5x3.5mm 0.5mm pitch QFN version of the 74LVC595 on.
It just worked. No pissing about, no having to finagle things, just printed solder paste, placed parts and reflowed with hot air. Worked perfectly first time. Just for a feeling of scale, the other parts are 0603, 0805 and the LEDS are 1206. The tracks are all 0.25mm.
It tested out fine electrically, no shorts, no opens, does what it was intended to.
The evilly small part in close up. Couldn't be happier with the joints.
I was expecting this to be an uphill journey in learning how to do it right and it turned into a walk in the park. I don't know quite what to do with myself now. At least I've got the otherwise identical HASL finished boards coming next week so perhaps I'll get my dose of finagling in on trying to make such a small part work on a HASL finished board (if it will at all).