It's a boy, girl, boy, girl...(Is my platy pregnant?)
As others mentioned, a separate tank while waiting for mom to drop the fry is probably your best bet if you intend on raising them
I am happy to announce 4 days after posting my "Is my platy pregnant?"
She gave birth. I followed the suggestions and put the mother in her own 14 gallon tank. When I got up at 5.30am she had been having them...and eating them. I saw her. So after that, I gently tapped the tank when she was about to eat one, and she stopped, see fish can be trained

So I am now the proud new owner of 25++ fry.
I did a partial water change the day before, her tummy was square (thanks so much for that clue!!!). I put a heap of that floating plant in there and spare filter surrounds(plastic grates for them to hide in).
I'm not sure how many there are until they are bigger.
She was dropping them over 10 hours from what I could tell. As soon as she was swimming around as normal, I put her back in the community tank, to carry on. she is well.
Thanks everyone who gave me suggestions, it certainly was invaluable, and I was successful in breeding my first fish
