I've seen a lack of UK support on the new Diet on the Go fad, but I've unearthed some British Alternatives to NS and the other diet delivery programs in the USA.
Choose any one of BodyChef's hamper plans (LowGI, Vegetarian, Detox, SuperFood, Premier) plus the caloric intake you desire, and have all of the food you need 5 days a week delivered to your door. If you live inside the M25, you can choose the CityDiet option, which is a 5 day a week plan CHOCK FULL of the freshest foods available and delivered to your door every Monday morning. You order all of your food in Hampers, and you need two hampers a week to fulfill your dietary needs for the 5 day week. A single hamper is anywhere from £43.50 and the weekly diets start at £87.50 per week. The best thing about this service is that all fruit and veg are included, so you are only responsible for Milk and water intake. The CityDiet ranges from £77.50 for a full 5 day menu-set.
The food is delicious and varied, but for a part time student like myself, the cost is not to die for. Here is a sample menu from the Low GI Plan:
Breakfast 2: muesli, low fat yoghurt & fruit
Lunch 2: wholemeal pitta bread, chicken cucumber & tomato salad
Snack: small portion nuts
Dinner 3: beef casserole with broccoli & cauliflower
Desert 3: summer fruits & low fat yoghurt
DietChef is great for the budgeted household. They charge around £50 (shipping included) for a full 7 day hamper. The choices aren't that widespread, mostly living off soups and granola, but you do get casseroles and other yummy goodies. Also, they allow you to swap your meals you don't enjoy for other varieties.
This is another diet delivery service in the UK, and personally, the choice of food and the prices are appalling. Costing up to £39 per day, all of your dietary needs are delivered fresh, every morning.