I’ve mostly resolved my issue now –
toolTip: { contentFormatter: function(e) { return CanvasJS.formatDate(e.entries[0].dataPoint.label, "DD/MM/YYYY HH:mm")+": "+e.entries[0].dataPoint.y; },
http://jsfiddle.net/4bc9v3hd/27/
Displays the text formatted correctly.
Could you point me in the direction of the colours etc to make it match the rest of theme1?