Thanks for the reply Charles,
The site doesn't have protected WHOIS. Nor does it have 1,000s of backlinks. It would be a 15 year old domain registered on BOTW & DMOZ.So it's very strange!
Google would know the author on Google+ and so forth. It wouldn't be a spammy website. It's a viable business in the training / education industry with 10+ staff.
There is something a bit fishy about the homepage screenshot on the companies SERP.
It's showing a PHP error and a blank white page. But on clicking the result the website is fine. Could this be to do with the site's last indexing? Google have indexed a error homepage which has effected the rest of the site? Note this is the only SERP that has this error.
Thanks for the help!