The pan crust and gluten free base are vegan. (All the others contain milk products)
The tomato base and all the veggie toppings are also vegan. So its 100% vegan if you swap the cheese for another topping. Here is the printed info from the 2014 dietary information booklet. The roasted veg pasta is also vegan without the cheese. So are the potato wedges, the ketchup, sweet chilli and BBQ sauces. All the veggies on the salad bar are vegan, as are the plain nachos, croutons and bacon bits. The salsa sauce and the low fat vinaigrette are also vegan. Every Pizza Hut has the dietary guide and are happy to provide for you if you ask.
Thanks to Polly Shave (a vegan thats works at Pizza Hut) for putting this together and letting me share it. The whole list is on the Pizza Hut website under nutritional information, then allergy info.
You might also want to view Wetherspoons Vegan Menu article
