Rebecca,
There are unlikely to be many people getting off the train at CH. It is a very rural station. Be sure to have a map handy if you intend to jog over to Barns Green - most of your jog will be on the route itself.
Enjoy the race - it's a varied course, in a sort-of figure of 8. You go through the start/finish at half way, which breaks up an otherwise quiet run quite nicely.