It sounds as though you have your work cut out here. If you're using the model standing orders, para 4d states that:
d The Council may appoint standing committees or other committees as may be necessary, and:
i. shall determine their terms of reference;
Para 5j sets out the business of the Annual Meeting, including:
v. Review of delegation arrangements to committees, sub-committees, staff and other local authorities;
vi. Review of the terms of reference for committees;
Check the minutes of last May's Annual Meeting to see whether these reviews took place.
It is good practice for councils to publish their policies and procedures on their website and if you have adopted the Information Commissioner's Model Publication Scheme (and if not, why not?!), it refers specifically to "Committee and sub-committee terms of reference" being available.