Apps only on US store

Charles Corker wrote:
...if I tried to download it direct from the US store

How do you plan to do that? You can change your iTunes Store to view the US store, but you can only buy from the US store if you have a US account (meaning a US billing address/credit card).

From http://www.apple.com/legal/itunes/us/terms.html:
+"Purchases or rentals (as applicable) from the iTunes Store are available to you only in the United States, its territories, and possessions, and are not available in any other location. You agree not to use or attempt to use the iTunes Store from outside of the available territory. Apple may use technologies to verify such compliance."+

It's not Apple's policy per se, but rather their enforcement of it. Logically, it's in their interests to sell an app wherever possible - they are a for-profit company, and app sales are quite profitable!

Restrictions by country are based on the developers' wishes and applicable local law, with which Apple complies.

So, contact the developer and urge them to make it available in the UK - or, if they inform you that they cannot for legal reasons, take it up with your government officials. Or wait and hope...