Hiya,
Thanks for the response, some really interesting ideas. It looks like it's just our site that is bouncing around in the serps.
I think point 2 is probably the most likely explanation. Although the site was built with SEO in mind, so the pages are all unique and with a good amount of content, we have a few issues with trailing forward slashes, which could be creating a duplicate content problem.
Basically the site is divided up into 9 sections - 7 of those sections are fine and ranking well, but 2 of them are bouncing around. Of the 2 that are bouncing around we have done some link building for just 1 of the sections.
I'll have another dig around in webmaster tools. If you have any other ideas in the meantime they'd be much appreciated!
Thanks
