Hi My recollection from my studies is that justification is a defence to any so called "slander and defamation". Whilst if you name the "establishment" they may claim that you are slandering them (to be honest are a kebab shop going to have the knowledge and/or the money to pay for someone who does) you can defend any such claims on the basis that there is justification for your comments - ie most people ate going to think that 27 people claiming to have got the trotskies after after eating there kinda means there is something not quite right. Problems you may encounter is the establishment saying they didnt eat there but till rolls will show that they sold things and what, by price, they sold.