Hi Nicola welcome to the forum.
If she doesn't want NH then I would leave it off the list. You can assume that the top 155 won't all want to go to CH and the rank numbers actually go lower than 310 because some children have other higher preference.
The only reason to include NH would be if she was prepared to accept it as an alternative. As far as I know there are no figures for the last ranked place accepted at each school. I have always found admin at both schools to be very helpful so it might be worth ringing to ask.
If you do find out then please let us know.