As mentioned below, FoI can work - I've just had a success with that although it did take 4 months so not quick and still not fully resolved.
Other option, as suggested below, write to each individual Cllr. If any / all fail to respond they could be breaching code of conduct by:
- failed to threat others with respect
- conducted them self in a manner which is contrary to the councils duty to promote and maintain high standards conduct
- prevented someone from getting information to which they are entitled by law
- bringing the their office or council into disrepute
- failed to give reasons for making a decision