For reference by others, a bunch of stuff I found on about.com when looking for the right words to start searching with - the perils of doing this online is I need words for the search engine at least to start off with!

Unfortunately these articles have an almost complete absence of photographs which is really unhelpful but they have descriptive text and will help you find search terms at least.

How to find your furnishing style. The difference between Formal and Informal is also described, but not on that page.

A list of decorating styles, linking to the articles about each: Decorating styles for home interiors.

Now I have words to start my searching with!