The copyright page is the same in the US, UK, and Australian editions and contains the following text and ISBNs:

“Published in large print in 1997 by ISIS Publishing Ltd... and Australian Large Print Audio and Video Pty Ltd... with the permission of Headline Book Publishing Ltd... Published in the United States by arrangement with The Berkeley Publishing Group”
ISBN 1-86340-758-8 (ALPAV Pty Ltd) [Australia]
ISBN 0-7531-5576-1 (ISIS Publishing Ltd) [UK]
ISBN 1-57490-107-9 (Thomas T. Beeler, Publisher) [US]

Whether you have a US or UK/Australian edition have in hand can be identified but the publisher name and/or logo on the back cover and spine. However I have been unable to verify a method for determining the difference between the UK and Australian editions.