The norm is tweed breaks, long woolen socks and climbing/walking boots. For above the waist, any breathable jacket in camo is fine. Assume you will get wet feet, so carry spare socks to change if you have any distance to travel st the end of the day.

Make sure your plus two/fours have long legs, or during the crawling, that goes with the territory, you will find your socks have parted company with your breaks. Also, tied garter are best, as they will anchor your trouser to socks without stopping your circulation!

Enjoy but expect it to rain on the hour, every hour😊

May I ask where exactly you will be stalking?