Oddly specific bus question about Hills Road College, Cambridge

Hi,

Looking for some experience here with the bus situation from Hills Road.

Youngest has just started at Hills Road and needs to get back to Longstanton P&R on the guided bus. The C buses at the end of the day so far seem to be too busy to let anyone on. Is there any point in ever trying to get a C bus home from Hills Road, or is it a waste of time and better to walk to the train station and get an A bus.

Thanks!