Andrew, take the A167 to the south of Durham, then take a right turn onto the B6300 Brandon road (might be an idea to have a map book with you).
After about 100 yards turn left onto a dead-end road over the River Wear and park at the top end.
Cross the cattle grid into the estate, follow the tree lined road over another cattle grid, up the bank and continue to follow the road around to the right until it takes a sharp left turn, the white Croxdale Hall gates are here on the right.
Set your birdwatching senses to full power
and watch the trees in front of the gates, you might have to stay for a while or you might get lucky straight away.
Plenty of other birds around to keep you busy. Good luck.