Once again John, you're coming to my aid with hints and tips that I really need!
I don't know where I'd be without the help of people on this forum and you're been one of the most helpful. THANK YOU!!
I'm learning so many little tips as I go along with this thing, it's great.
My veneers are actually 25mm wide, not 15mm, so you'll imagine how much a pain in the back side they can be - they split, warp and crack.
I've got around the problem of tiny cracks in the veneers by staining some filler with mahogany woodstain, and just bunging it on!!
I considered Madboatman's suggestion of filling the gaps with the edge of another strip of veneer and then sanding it flat - that would've looked very good, but the gaps were irregular length, and very thin, perhaps too thin. I don't know how I managed to do it, but some were only about 1cm long, some were 5cm or even 7cm. All of them were under 1mm.
Once again John, thank you so much for chipping in. Keep the help coming!
All the best, Julian.