Some info on vegan options at the University of Essex, from a lecturer who works there:
Fusion restaurant is quite good, they change the menu a bit but they do various stir fries with tofu and vegetables. They can customise as you like.
Zest has a hummus flat bread, and a tofu and vegan pesto panini.
Happy days has a veggie burger
Take three has a hummus and salad baguette (sometimes) and a peanut butter sandwich (good breakfast).
There is a salad bar in Blues open til 2pm and they do jacket potatoes and beans. It is ok on campus for vegan food and it is getting better, but you usually have to be quick because sometimes these things run out by late lunch time. If you want anything about 4pm onwards they may have sold out.