The solution to this original posters problem is to create an amazon.co.uk account, if he or she doesn't have one already. Goto the 'Kindle' section of the store, and somewhere along the top of the screen is a link to another page where you can manage your Kindle account. In here you'll find the option to change your county setting from the default, 'Ireland' , to 'United Kingdom' instead. You'll be prompted for an address, but you can pretty much make up ANY address so long as there is a valid postcode to go with it. Just google 'UK postcode example' for ideas. This has worked for me.
If you have a PC, you can now elect to download the Kindle book titles at UK prices to your computer/laptop and read them off the screen using the Kindle PC reader application. You can also follow the guide at http://nyquil.org/archives/1235-Conv...-Possible.html
that will let you decouple the DRM from the book and then easily convert to a format that a Sony device will work with, using software called Calibre.
*I think you need to be using an older version of the Kindle PC app to get this hack to work. Try googling 'Kindle PC old version'. You wouldn't be losing an enormous amount of functionality by using a slightly older version, don't worry.*
Using this method, you'll save a lot of money off the cost of buying books from amazon's competitors at ridiculously over-inflated prices and still enjoy on your favourite device.