I've added some new tools to my
website - one for authors, one for readers in the UK.
First, for authors:
Create Apple & Amazon Links for any Country will create a link that redirects to your book page on the Amazon/Apple store in the user's country. (UK users go to Amazon UK/Apple UK, German users go to Amazon DE/Apple DE, etc)
For readers in the UK:
View Amazon.com Page at Amazon UK is a bookmarklet that you drag to your browser's bookmark bar. If you're viewing a book on amazon.com, it'll take you to the book's page at amazon.co.uk. If you're happy editing the JavaScript, it's not difficult to tweak it for other countries.