Thanks all for your responses, much appreciated. Really grateful for your very in depth response too, Thomas.
Thanks for confirming the loading and code issue. As I say, I didn't make this site. I've worked with WP for years but there's only so much I can do within the price I charge for SEO - I will of course make this recommendation as chargeable work.
I've noticed that some of the directory listings have added 'www.' in front of the link. The website is without www. So I guess that could be affecting this. I've submitted to at least three directories which have links to the site.
Thanks again.