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Thank you so much Gianlucca! Lots to take away and get fixed.

Great addition of Jonathan! I also think a well implemented example will not get affected by this update but identical pages won't do you much good in the future. So if you start with this strategy, make sure you do it good!

Excellent, that reference is just what I needed, thank you!

If you are not changing the IP address you don't need to change the DNS, if you change the IP address, in addition to updating the DNS records you also need to properly redirect traffic from old urls to new urls. With IIS the best option is using url rewrite, which is very flexible but a little tricky to set up if it's the first time you do so: http://www.iis.net/learn/extensions/url-rewrite-module/creating-rewrite-rules-for-the-url-rewrite-module Url rewrite does operate at web server level, its powerful and does the job, but you may consider doing redirects at application level, depending on the technology you use, php/dotnet/aspx/mvc you have different tools. The advantage of doing it at application level is you can redirect dynamically, in other words use an algo to translate the old urls to the new ones using whatever information is stored in the application cache, database, and so on. While using IIS url rewrite you either statically redirect each old url to a the new url or you use regular expressions or wildcards to dynamically do so. In other words using url rewrite you have a little less flexibility.

Attributes and their corresponding values can be in any order within a tag. Having a self referring canonical tag also helps eliminate duplication issues if the site produces query strings appended to the URL. There is no ambiguity as to which is the "real" URL.

It may be difficult, particularly if the .com is also a well established brand in the UK.  That being said though, it isn't impossible to have your client rank in the SERPs as well for the same brand if you can establish them as a brand entity with Google. For example, here is a search I did for Peak Auto, a well known, established brand in the automotive supplies industry- http://screencast.com/t/ycYugMK876  You'll see there are two other local results in the mix of primarily Peak Auto results. Another example is to search for "Merck" in the .co.uk Google.  Some results will be from the US-based company of that name, the other results will be the German company of the same name.  And interestingly both are drug manufacturers. So it may not be an easy task, but it certainly isn't impossible.