There are threads about this already (see the one regading eBay fiddling again). I wasn't having the issue, so I fiddled around last night trying to get the foreign login and eventually succeeded. When it gives you the foreign page, change the .de or whatever in the address bar back to .com.au and hit enter. When you then click on continue on the next page, or you go to your messages, it will revert back. Change the address again to .com.au. Once you can get it to English in your messages, it should stay in English to read and reply to messages. You might just need to change the address bar a few times to get there.
During my fiddling last night to trigger it, it was actually clicking on My Messages in the My eBay dropdown at the top that did it, so that may not be a workaround for everyone. It was the only way I could trigger it. I'm back to English this morning with no problems.
