I created a seller account on amazon.co.uk, and want to send out a small package to test out a product (20 units)
UPS seems to be the most popular, but they're quite pricey. Does anyone know if USPS priority international would work well?
Talk with the folks at MyUS.com about your situation.
Likely they'll be able to provide a simple + cheap way to handle this.
And... overseas shipping is always expensive, so depending on your product, profit margins may not allow selling through overseas Amazon organizations.