Make sure that there are no containers on your page that are overlapping your gallery.
If this is the problem, you could try to bring the gallery to the front by settings the 'z-index' of the gallery container to something high (like '99').
Also, this is not likely to be the cause of your problem but your <iframe> code should have quotes surrounding the attribute values.
<iframe src=http://www.stevenbaileyphotography.co.uk/wedding-gallery_files/weddinggallery-index.html width=800 height=600 frameborder=0 scrolling=no></iframe>
<iframe src="http://www.stevenbaileyphotography.co.uk/wedding-gallery_files/weddinggallery-index.html" width="800" height="600" frameborder="0" scrolling="no" style="z-index: 99;"></iframe>
SimpleViewer Support Team