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Hi,

You have a large number of pages of very similar content targetted to the locations you serve. I'd look at the traffic to those pages and see if there is any evidence to suggest some or all of these have been devalued recently? Since low quality pages can now influence the rankings of the whole site (post google panda) you may want to seriously consider condensing those pages into one.

http://www.clairehegarty.co.uk/preston-hypnotherapy
http://www.clairehegarty.co.uk/southport-hypnotherapy
etc...

Edit:

You also seem to have a number of duplicates of your site content on domains like http://www.chesterhypnotherapy.com
http://www.cardiffhypnotherapy.com
etc...

How is your traffic on these domains?

Unfortunately you can't change crawl settings for Google in a robots.txt file, they just ignore it. The best way to rate limit them is using custom Crawl settings in Google Webmaster Tools. (look under Site configuration > Settings)

You also might want to consider using your loadbalancer to direct Google (and other search engines) to a "condomised" group of servers (app, db, cache, search) thereby ensuring your users arent inadvertantly hit by perfomance issues caused by over zealous bot crawling.