For anyone who has had the same problem, I fixed this by adding the following script to the theme itself (which in my case was in script.js in the /js folder). . .
if ($ (‘.product a’).length ) {
var wooCommercePhotoSwipe = $(“.product”).each(function(){
$(this).find(“.zoom”).photoSwipe({ allowUserZoom:false, zIndex:’10000′, captionAndToolbarShowEmptyCaptions:false });
});
}
It works perfectly now. Hope this helps others.