I have found a site listing Uk benchmarks dating back over 100 years, I have been unable to find a way of logging them. many of them are plaques on church walls and are still intact. would be nice to be able to incorporate it into geocaching. Here are the sites if anyone is interested in taking a look.
http://www.bench-marks.org.uk/lrindex
http://www.movable-type.co.uk/scripts/latlong-gridref.html
[/b]sorry posted twice in error