Brinsey's Well (spelt with an extra 'd' on OS maps for some reason) is one of several ancient wells in the Staunton area in the Forest of Dean and was a main source of water in the village until 1931 when mains water took over but the well still remains. It is thought to originate from a Saxon farm/homestead but I couldn't find out for certain.
This spot is especially nice on a sunny day but I'm pretty sure I wouldn't want to drink any of the water now! 
Parking can be found in the village but if you're having trouble getting close you can use the parking waypoint which is a side road, but you will have to cross the main road to get to the cache site (it's not that busy!). Access to the well is on short footpaths from the north or east and the cache is a large micro that should be pretty easy to find.