you don;t realyl need to know do you. All you need to know is what you can or can;t put in them and what bin yuo should put them in when full.
If they are classed as compostable then they are made form food stuffs.
Bread wrapper bags are apparently not recclable and similar in non recyclability as the black platic microwave trays. Which I find odd surely a bread bag can be made recyclable.
I do wonder whether the paper they use in my chippie is recyclable or not. But I won't worry too much as I've only been there twice so far this year.