Is anyone using machine tags/triples for National Grid references?

I'll post this around the various lists but I am still thinking about how best to phrase it. I'm not a geo-geek and I'm never quite sure if I'm using the right language to describe whatever it is I'm talking about.

We've been having more conversations about how we can use tagging to publish more information about LAARC photos. This would allow us and our users to explore, use and compare site photos in lots of different ways. Eventually it may also be applied related data streams such as archaeological finds/museum objects and related media, but for the moment we're just exploring what we can do with an existing platform like Flickr.

Using machine tags to add latitude and longitude looks simple enough, and seems there's a de facto standard for geo:lat and geo:lon. But is there a similar de facto (or proper) namespace standard for machine tags for UK National Grid references? Leave a comment or email me if you know of any, or even if you're just using them yourself.

Some relevant links:
Flickr: Discussing Machine tags in Flickr API
geobloggers » Advanced Tagging and TripleTags
geobloggers » Flickr Ramps up Triple Tag (Machine Tags) Support.