I sent a few letters a couple months ago to Georgie Henley, Ben Barnes, Anna Popplewell, and James McAvoy (via venue, since I know he usually sends preprints). I was able to send them from the US to the UK/Canada with international postage, however, I couldn't include postage from the UK/Canada back to the US on my SAE, as its not sold where I am (nor are IRCS).
![UK [uk]](./images/smilies/flag_uk.gif)
Thanks for reading!