30 weeks and my work haven't spoken to me about maternity?

Keep asking my work to have a discussion about maternity.
Handed in all my forms, I'm just worried as my baby is breach, my desk job I've had no risk assessment for my chair/back I'm in pain, and I'm getting bigger.
I'm in the UK so I have to give 28 days notice. But when I asked to speak to them about it they never have time..
The longer they do this I just want to leave more and more, I need a date.
What can I do?