Code added to top of site

Hi all,
Really REALLY strange one.

If I visit my website, (using Chrome V25.0.1364.160 on iMac) all is good. If i search for the ‘Belmore Centre’ in a Google search still in Chrome, and click on the home page link, it places a whole other web page at the top of my website?!

But, repeat search in Yahoo, again still in Chrome, all good. Repeat exactly the same search in Safari, yet again, all good?! In fact the only time things view ‘wrong’ is clicking on the home page link after a search in Chrome!

This is playing havoc with the search results for my site as you could imagine! You can see from the search results it displays in Google or Yahoo, The opening paragraph is nothing to do with what’s on the site!

I’ve checked site for Malware, none found and all plugins are up to date. This problem happens on all colleagues Mac’s and PC’s so I know it’s nothing nasty in my OS.

Any help would be gratefully received, it’s driving me nuts!

Andy