Thanks Fellas. I've printed out the links above kindly posted by Gearbox, so yes, time to try old spokes and nipples in the rim and get some handle on the angles. Not so simple as I thought, but not that hard either. As a pusher I'm not too worried about a bow here and there and it will be a good to have a go at wheel building......more a thoughtful pastime rather than a greasy one. Cleaned up the old rim, true to form no identifying marks so it's trial and error for now.
Cheers.
Swarfy.