Used to play in them as a child in the 60's, there are also a lot in the area of Hook pit Farm lane from Kingsworthy towards Worthy down Railway halt. there is / was at least one along the old dissused GWR line , between Worthy down and Kingsworthy junction. several in the surrounding fields.
Could that cast link not be a mount between the MG and the Tripod stand, it looks similar?
Bill - this may bring back some memories -
[ame]http://www.derelictplaces.co.uk/main/showthread.php?t=16028[/ame]