Unless you eat wisely in a carvery or traditional English restaurant you could eat in excess of your calorie and fat intake in one sitting. Avoid fatty meats and pick carefully ensuring you have a good balance of protein, carbohydrate and vegetables. Be conscious of the cooking methods, grilled, steamed, poached and baked are far better than fried.
Supplement chips of fries with a jacket potato or a salad. Ensure there is enough vegetables with the dish. Avoid pate and rich dressings, for example in a prawn cocktail on starters and choose a fish dish or grilled or roast chicken as main. If the carvery is unlimited make sure you exercise restraint.