Google and Bing Maps opening in the wrong location

When I open Google Street view or Bing maps from my Geocortex viewer, the location is always out by a 100 metres or so.

I'm fairly sure this is down to the projection of the mapping used in the viewer, which is British National Grid. I'm guessing that the coordinates that get passed into Google/Bing are in Lat/Long format, which then causes an offset to the location that I am trying to open.

Is there anyway that this can be resolved, so that the location in the viewer (BNG) is accuratley reporjected in Lat/Long before the coordinates are then passed to Google/Bing?

Thanks,

Aled