I live just a couple of miles away from Hardwick too... thats cool!, i grew up in Pilsley but now live in Clay Cross, during the summer months Hardwick Inn is my favourite place to call after a walk around the ponds.
I've never been on the Rowthorne trail before though, is this the trail that runs around the back of the hall accessed from the gate halfway up the steep hill (from the road that takes you through the park?) I've never seen a snake in the wild, your so lucky. I'm definitely intrigued to find the trail and take a look in the summer when they may be out and about.
Thanks