Hi Nick, Just finishing a near-identical project in Charente Maritime - 36 sq. metre ground floor room, old floor rotten in parts, joists rotten through where they were in contact with the stone. Floor and joists ripped out, 'aggregate'/hardcore laid, sand layer, compacted, termite treatment of soil, vapour barrier, 7-10 cm of concrete (plastic fibre reinforced i.e. not steel mesh), joists for new floor and a chestnut plank floor laid. The main differences with your project seem to be the area, and whether or not you will be installing a wood floor or whether the concrete base will have to come up higher for tiles i.e. bigger or smaller volume of aggregate filler. Our floor was about a foot above the ground. Let me give you the total cost and then identify the items that may differ. Total cost was 3970 Euros. This includes eight days labour for one person (local builder at 140 Euros/day with me as the skivvy)(It took four days to strip the old floor and lay the concrete base, and another four for two of us to lay the new wooden floor). Wood for new floor was 1300 Euros for 36 sq m. Cost includes 11 tons of aggregate (course and fine), 3 tons of sand, cement, battens, fixings and the rest of the materials and also includes hire of a cement mixer. Hope this helps. I say 'just finishing' - the work described was done last summer but the floor is not sanded or varnished. Sanding is scheduled for tomorrow.