The ones that i've had have been made of soy and gluten and wheat with spices (not sure what exactly but i think pepper or chillie was involved)

Rusks textured soya spices and flavourings.

They can be made from lots of different ingredients, here are some...

http://www.webvalue.net/recipes/sausage.htm

The ones I have cooked for customers are made from soya, one thing I can't understand is why if you are against eating meat is soya produced in such a was as to make it look and taste like meat.

I have tried a vegetarian sausage and to be honest it tasted just like a pork sausage

There is a vegetarian protein called quorn that is ideal for this. Tastes like chicken.

Soya protein, but have a look at a box int he supermarket. Then you'll know.