Who to talk to about advice before filing a form J?

My mother’s landlord is a leech and is trying to blackmail her into an illegal 30% rent increase. (“Agree or I won’t renew”) but based on my brief chats with tenancies, her even being fixed term is possibly not legal as she was periodical for over a decade and he bullied her into signing fixed term.

Before we file a form J I’d love to talk to someone about how the process really works, what to have prepared, etc. what the odds are of a decision in her favour, etc. my mom is terrified she’ll lose her home, she’s trying to get into a seniors building but has to wait for space.

We are broke folk, so cheap or free is ideal. We probably don’t qualify as “low income”, but too poor for lawyer money.