I'd totally do it. My eldest is 9yo and I'd have no qualms leaving her in your situation. I used to walk home from school (20min walk) and kick around the house until Mum got home from work when I was 10/11 years old. I was also often left home alone of an evening/night time from 8 years old when Mum worked evenings in a bistro.
But I admit to being a pretty relaxed, free-range type parent