Thanks for the help. I'll definitely try my local wood yard when/if I try building a large hull for R/C this way, though currently I only need enough for a hull about 32cm long and 7cm deep.
I'll probably try buying some decent-quality 1.5mm ply and cutting strips from it. Since the finished model will be painted and coppered, the unpainted appearance of the wood doesn't matter much. Annoyingly, I've got quite a number of decent quality obechi strips left over from Billing Boats kits, but they're in 3 different widths and there isn't enough of any one type for my model.
I did try using coffee stirrer sticks, just to see if it would work (using several sticks for each row of planking) but they're no good at all - apart from being poor quality wood, prone to breaking + splintering, and nowhere near flexible enough for hull planking, they're also irregular in width, no two sticks are quite the same width and some vary in width along their length, whilst others are warped. They're OK as a cheap source of wood for structural work but no good at all for hull planking - a pity since £10 will buy virtually enough to plank HMS Victory!