Thanks all!
Those who think these are too difficult really should have a go - because they actually are quite easy - but the effect they give makes it look hard to do. The cubes are not difficult either, the 3D effect comes from the placing of light, medium and dark fabric. They are just hexagons like the other blocks.
There are so many things you can do with them, I find the hardest bit is making a decision. When I've done the blocks I "play" with them on the wall for days until I'm happy with the result.
Go on - have a go...