As a long time amateur archeologist, I can tell you that we don't give out places to hunt. Its just like a fisherman telling you his fishing hole. I will tell you there was a LOT of troops in and out of Oxford. You need to do your research to locate places to hunt. Get some old maps and then put boots on the ground. Be sure you check with the landowners before you go into a place.
I would start with the Official Records, find out what units were there and then try and find regimental histories, diary's etc that will help narrow it down. The 3 keys words to finding spots to dig are, Research, Research, Research.