Yes, this can actually be done fairly easily. Using the Solution Explorer, open up the "Properties\Settings.settings" file, which specifies the default settings for the application. Change the Value of the AmazonLocale field from "EN" to "UK". That's all there is to it.
It is probably well worth your time exploring how this value is accessed in the code and used to determine which Amazon web service URL (soap.amazon.com, soap.amazon.de, soap.amazon.co.jp, etc.) to contact with requests. Take a look at the GetLocUrl() method in the SimpleAmazonWS class in SimpleAmazonWS.cs, and the other methods that use GetLocUrl().
As it turns out, the Movie Collection starter kit uses the same web service URL (soap.amazon.com) for both the EN and UK locales. If Amazon actually has a separate soap.amazon.co.uk service, you could set that up in the Settings.settings file as well.
Hope this helps!
-Tom Meschter
Software Dev, Visual C# IDE