I've never heard of them, so I took a quick look at their website. Their food looks very tasty and has good ingredients. I assume you're in England? I don't know about losing weight with their food, since you would also be eating other foods during the day, but they could be useful for people with food allergies.
I prefer to cook my own food, so I know exactly what I'm eating, although I also have some convenience foods on hand for when I'm in a hurry (or lazy).