Just trying to be helpful - this map http://www.hants.gov.uk/walking/hangers/section1.html says they are medieval? They don't show up as scheduled monument on the Magic map site (blah blah blah rhiannon and her Magic map yeah yeah yeah).
This page http://www.hants.gov.uk/hampshiretreasures/vol06/page046.html
has a little more.

I'll get on with some work now.