timwarr.net

var locations = new Array();

var xy1 = new MMPoint(523000,212324); // OSTN97 OS National Grid
var xy2 = new MMPoint(323000,212324);
var xy3 = new MMPoint(423000,212324);

locations.push(xy1);
locations.push(xy2);
locations.push(xy3);

var funcRef = convertResultsLoaded;
var converter = new MMConverter( funcRef );
converter.convert(locations, ‘osng’);

function convertResultsLoaded() {
console.log(converter.result_set);
};

A while ago I blogged about using OS Grid References in the Multimap API.  Web mapping developers [...]

Multimap API supports grid references