Hadleigh and Thundersley are both Saxon names. The “ley” part is generally thought to be late Saxon in origin.
Hadleigh means heath clearing.
Thundersley may well mean Thor’s clearing.
Excavations at the site of the old Hadleigh Crown Inn pub garden in 2015 revealed pottery dating back possibly to 1000AD, ie in the last period of the Saxons before the 1066 Norman Conquest.
The above shell tempered cooking pot was found by AGES AHA about 80cm below ground. The complete pot would have been about 21cm diameter across its rim.
Nearby, just below the level of the pottery, 3 post holes were revealed. Probably too small to hold a main building post, but maybe a Saxon internal or external timber frame stucture.