At last I’ve managed to find this elusive long barrow, after about the 5th attempt. It is in dense beech woods north of the other long barrow nearby. This barrow is generally listed as Vernditch Case long barrow, the other is usually listed as “long barrow south west of Vernditch Chase”, but what’s in a name?
The barrow itself is quite slight and difficult to see, I’m happy that this is it, as it is in the right place. However there are various bits of Grim’s Ditch in this area and I have seen photo’s that purport to be the barrow which look more like the ditch, i.e. much too long and thin. This is one for completists (like me, I suppose) as it is small and has probably been ploughed in the past.