This site was very easy to access. Heading west towards Ashdown House (N.T) along the B4000 from Lambourn you come to a small parking area which has several public footpaths leading from it (about 1 mile before you reach Ashdown House). Park here.
You will see a footpath running north and south and a path running south east (behind the trees next to the road) – this is the path you need to take. The field on your right is fenced off and the barrow is clearly seen in the corner of the field straight in front of you. (The barrow is actually visible from the parking area). When I visited the grass was high around the barrow but it was easy to spot with a large squarish stone sticking out of the top. There were various other 'lumps and bumps' in the field but I don't know if these were smaller barrows or natural? O/S map only shows one barrow.
There is what looks like a standing stone to the left of the barrow amongst the trees but I assume it is natural as there is nothing showing on the O/S map.
Whilst visiting the site it is well worth continuing along the B4000 towards Ashdown House to see the field full of erratic stones on the left before the turning to the House. It is very reminiscent of the surviving fields of stones found around the Avebury area.