Can't do much at the moment as I'm not in the UK but the co-ordinates of the Sphinx should be obtainable from the AERA survey and the diagrams and scans published in the survey that was done just of the Sphinx for an international symposium in 1992. I'll have a look when I get home. I took my own readings as well but couldn't get into the actual Sphinx enclosure but did record points all around.

The stadium, or what was left of it, was still there in February and has been an eyesore for a few years as it was left half demolished. I took some photos in the area. But can't access at the moment.

Jon