The first job was to finish the walls on the front using the thermalite blocks. The front is a real patchwork quilt, as I was using damaged and broken blocks. I tipped all my vermiculite into this hollow cylinder. I used 6 bags, so the oven has 6" of vermiculite at the bottom, and about 18" of vermiculite around it at the top. Plus the 4" of insulating blocks. The top is open at the moment, to help with drying it (it's covered by the roof anyhow).
The back of the oven won't ever be seen, so I decided to have a go at rendering it. I was really dreading this, as I've tried plastering before and made a dreadful job of it. This time I used a 4 parts grit sand, 1 part cement, 1 part hydrated lime mix (first time I've ever used lime, and got a lovely cement burn on my hands because my rubber gloves leaked). It went on like peanut butter, and stuck beautifully. The lime makes an enormous difference to the 'stickiness' of the mix - it also helped that I'd coated the blocks with a dilute PVA solution too. I was so pleased with this that I considered using it on the front of the oven too. I still can't believe I did this - it was much easier than I had had dreaded.