A lot easier to find than I was expecting.
From the A436 take the minor road north towards Chastleton. Just past the entrance to a farm (on the right) there is a lay by you can pull into on the left. From here walk west through the trees and you come out into a large field. Keep wallking east a short while and you will see the Long Barrow.
The Barrow itself is now a scrub covered mound approximately 1.5 metres high x 20 metres x 30 metres. Amid the scrub are several large stones laying about.
There are tremendous views to be had to the west. A great spot for a Long Barrow.
The long barrow on Adlestrop Hill was excavated in the 1930s. As the article in the accompanying link nicely says, it was discovered by Major R C Freer and his sons, who were out blackberry picking in September - they noticed the stones of the chamber poking through the mound of turf.
The barrow's stones can still be seen at the east end of the mound (it's only .8m high here, but 1.5m at the other end).
A single paved burial chamber was found, which contained the remains of about 8 people. A cairn of stones had been piled over and then the whole covered with earth.
The local natural limestone would have been easily gathered - they're known as 'Rugg Stones' and renowned as a pain to ploughmen. There are mounds of field clearance in the same field as the barrow. The article mentions that the stones in the rockery at Adlestrop Park probably came from this hill. So this means the hill is the source of the Goose Stones too?
(info from the smr record on Magic and the article in the link).