Here's what I use for the US version of Amazon. I'd guess it'll work to just switch the .com portion of the URL to .co.uk.
<Link version="1.1">
<Item Name="Name">Amazon</Item>
<Item Name="Filter"/>
<Item Name="Action">1</Item>
<Item Name="Base URL">http://www.amazon.com</Item>
<Item Name="Search URL">http:////www.amazon.com//gp//search//ref=sr_nr_i_0?rh=i%3Apopular%2Ck%3AReplace([artist], ,+)&keywords=Replace([artist], ,+)&ie=UTF8&qid=1263910815</Item>
</Link>