Thank you everyone!
Andy - I'm glad you clocked them as breeze blocks, I had a few moments... I like your idea of using the breeze blocks as a foundation course, I'll have to give it a go. I will be making more and I think I will be experimenting with all sorts of materials, the idea is to create a range that might make up the main drag of some wigged-out desert planet. This will probably be one of the more (in game) solid buildings.