To my astonishment I've spotted what I've (perhaps boldly) assumed to be a standing stone whilst on a train. It's recorded on OS outdoor leisure map 14 as "the broadstone" and it looked like a megalith to me so I've posted details below.

http://www.themodernantiquarian.com/browse.php?site_id=3110

The site is actually in England but I've posted it in S. Wales/Borders as there are a number of nearby sites in that region.

Any one got any info on this stone? If not I might see you there next weekend ;-)