Ledger is selling on Amazon (and it's the only merchant selling on amazon.com, .fr, .de, and surely .uk too) So it depends. You can be buying from the original seller but on different e-commerce platforms. With Amazon's extensive logistics, it's even an advantage for them, Amazon is doing the job for shipping.
Amazon often stocks and ships products from third party sellers too. Most people don't bother checking that. They just assume it's straight from Amazon themselves.
I wouldn't consider anywhere other than direct from their own websites.