openlayers 2 - How to set Zoom Level based on Overlays in Ordnance Survey Map?

I am using the Ordnance map as a backdrop in my website. when overlays the WMS from Geoserver, I am unable to increase the zoom level. Please see my code and kindly suggest it.

 var options = {

                maxResolution: 0.55804443359375,
                projection: "EPSG:27700",
                units: 'm'
            };
            map = new OpenSpace.Map('map', options);   

// Define or get the vector layer to be used
var vlayer = osMap.getVectorLayer();
var mlayer = osMap.getMarkerLayer();
vlayer.displayInLayerSwitcher = false;

mlayer.displayInLayerSwitcher = false;


// setup tiled layer
format = 'image/png';
var tiled = new OpenLayers.Layer.WMS(
                "Oxford_Example",
                "http://192.168.0.126:8080/geoserver/cite/wms",
                {
                    transparent: 'true',

                    LAYERS: 'cite:Oxford_ExampleCapture',
                    STYLES: '',
                    format: format,
                    tiled: true,
                    tilesOrigin: osMap.maxExtent.left + ',' + osMap.maxExtent.bottom
                },
                {
                    buffer: 0,
                    displayOutsideMaxExtent: true,
                    singleTile: true,

                    ratio: 1,
                    isBaseLayer: false,
                    yx: { 'EPSG:27700': false }
                }
            );


osMap.addLayers([tiled]);



//Show Co-Ordinate on mouse over    
osMap.addControl(new OpenLayers.Control.MousePosition());

//OverViewMap
var control = new OpenSpace.Control.OverviewMap();
osMap.addControl(control);
control.maximizeControl();

//ScaleBar
osMap.addControl(new OpenLayers.Control.ScaleLine({ displayClass: 'olControlScaleLine'   }));

//    osMap.addControl(new OpenLayers.Control.Scale({ displayClass: 'olControlScale' })); 

//Layer Switcher
//    var layerSwitch = new OpenLayers.Control.LayerSwitcher();
var layerSwitch = new OpenLayers.Control.LayerSwitcher({
    div: OpenLayers.Util.getElement('layerswitcher')
});
osMap.addControl(layerSwitch)

But i can zoom in this level only. I am unable to the particular feature. See the below image: