Nice looking build - I built a block shed with my dad, but we never did the insulation in the slab. It's more of a home to a couple of motorbikes, several mountainbikes, with a workbench, cabinets & shelving taking up the rest of the space!
We did run electrics down to it from the house, and have the armored cable coming up through the slab - setting it in place before pouring the slab in sections - mixing the concrete ourselves.