That's not correct. iBook works with the ePub standard and is able to read any ePub book from any online e-book reseller. Just look around in your country for a store that sells this format and you can be sure that you can sync your ebooks to the iPad.
It's true though that the books in the iTunes store will not be available globally but there is the alternative described above, which should work just fine.
It is correct - the iBooks app is US-only according to the Apple website: "1. iBooks is available only in the U.S.". There is no mention of it at all on the UK Apple website.