The biggest threat is saturated fat as we eat nearly a fifth more than recommended. The worst culprits are pork pies, sausages, full fat dairy products, butter, cakes, pastries, etc.
Monounsaturated fats are actually good for us. Along with polyunsaturated fats they help to stop the arteries furring up. Monounsaturates are found in olive oil, peanut butter, avocado, nuts and seeds, while polyunsaturates are found in sunflower oil, nuts, low-fat spreads and oily fish. Healthier, yes, but they still contain as many calories as saturated fat.