Well make sure you do not mention your employer's name or company name in court! If you are asked if you are in employment just say eg" I work in a freight company" .Put your request to be accompanied to the disciplinary in writing to the union rep or email. If you get no reply, go on the internet and find out who the regional officer is. Have your membership no' if possible.
Personally I would have only told the employer after the case had gone to court and then only if I was found guilty.