Hi,
Paul has asked me to write to you.
You mentioned Peterborough Crescent as a closed station from the GN main line to the Northampton line but that station was a "Midland Railway" station and not on the line of route. I suggest that the next station instead of Castor should be Orton Waterville which was on a different site to the present Overton (formerly Ferry Meadows) station.
Regards
Brian
aka Steamybrian
And if I forget, Birthday wishes to you