Meat costs a lot of energy to produce, and cows in addition also produce the greenhouse gas methane. Generally, poultry and fish are less harmful to the environment, and most people in the UK eat more meat that necessary for good health. Generally, we eat more meat than recommended – Link.
Thus, both for health reasons, to save money and protect the climate it is good with a couple of meatless days during the week. An added benefit is that after a few weeks, you will start to enjoy vegetables more, and in general, start to eat healthier.