I always camp in the americas field, and when I first started going to W+P there were loads of toilets in the field, they were in blocks of four placed over the field.
The reason that they smell and are dirty is that they don't get cleaned enough for the amount of people using them.
Every year I tell rex the same thing about the toilets and every year the reply is the same, "i'm sorry, we are going to use a different supplier next year and they will be better". but every year they are the same.
When you go to W+P this year, have a look and see how many people hire thier own toilet, it proves the point.
Rant over!