In a large skillet, heat olive oil over medium heat and add the mixed mince meat. Break it up into chunks with a spoon and season generously with salt, pepper, cinnamon, and oregano and brown the meat.
Add onions, green pepper and garlic and cook until onions have softened.
Add tomato sauce, red pepper flakes, ketchup, water, and Worcestershire sauce to the pot.
Reduce heat and simmer for about 15 minutes and taste for flavor. Adjust the seasoning to your liking.
Remove from heat and stir in chopped Kalamata olives and crumbled feta.
Serve on toasted buns.