In short- no.
A recent case heard in the Employment Tribunal of Conisbee v Crossley Farms Limited decided this very issue. Under the Equality Act 2010, workers are protected from being discriminated against on the grounds of their religion or beliefs. In this case, the claimant claimed that they had been discriminated against on the grounds that they were a vegetarian. They stated that they had a genuine belief in vegetarianism and animal welfare.
However, the Tribunal decided that vegetarianism did not amount to a philosophical belief under the definition in the Equality Act. The Tribunal decided that it was merely an opinion based on logic and that in order to be protected, the belief in question must have "similar status or cogency to religious beliefs".
Interestingly, a different Tribunal will soon rule on whether ethical veganism is capable of being protected as a philosophical belief. It will be particularly interesting to note whether this decision is taken into account by that Court.