Cheers for the advice Jozef, hopefully I'll remember that when I come to put it all back together!
I managed to blast the ally housings during lunch today at work and reassembled the starter motor minus bolts (which are still being rust treated) when I got home this evening. I used hammerite satin black spray paint on the motor housing and solenoid after first degreasing, stripping the old paint and treating/removing the rust. It's come out pretty well although I am missing a small screw

If it doesn't turn up I'm sure I can replace it easily enough at work.
All parts stripped, degreased, blasted and main motor shaft bearings both replaced:
Starter motor reassembled minus bolts:
I've decided not to bother laquering any of the aluminium ancillaries but I will no doubt paint the block and gearbox and repaint the rocker cover. I had a brief search through a thread on Honda Tech full of frankly awesome rocker cover paint jobs. I'm not even going to attempt to compete with them but it's made me think just plain wrinkle red is a tad dull. I may paint it with a heat resistant primer then put pirates black over the top with polished DOHC VTEC lettering then a layer of lacquer but we shall see..!