Two ways of doing it ,One
would be to dig strip foundations all round ,concrete footings, block up to damp course ,(150 mm above ground leavel)
dig out floor 250 mm deep ,put in 150 rejects wacker plated down , blind over with building sand lay a DPM , and 100 mm concrete over site , you can put mesh in if using heavy jacks or machinery
Two
Dig out your base about 300 mm dip ,shutter around , put in 150 mm hard core , wacker plate , blind over with sand , lay DPM ,Lay mesh on 50 mm shoes , lay 150 mm concrete