Realised I hadn't updated this in years, so here is a potted history of 2015 to today...
Windows in and a coat of primer on the outside.
Starting to add the insulation on the inside. Floor is still gravel/dirt.
Floor structure in, compacted substrate, breezeblocks and then insulation, a Damp proof membrane, and chipboard.
Painted the inside of the doors and the outside is now Blue & Black.
Next layer of the floor, recycled industrial pallet wood, 2.5" thick x 6" by about 10ft. Enough for the entire floor was about £80. It was a serious amount of wood for the money!
Outside looking great in the sunshine
Paneling the inside, a lorry load of T&G. And lots of cutting!
Winter and, though you can't see it, it now has a corrugated metal roof. I know that because the spare sheet is lying on the lawn in the photo!
Latest photos of inside, Its been up now for 3years and the interior is still perfect. I was worried about it getting damp, but so far so good.