Londonite,
Sorry it's been so long, but I toddled off to the good ol' US of A for a couple of weeks.
It's an automatic approval, so you needn't wait for a reply from the IRS. Just include a copy of the extension with your return when you file in October. If you return home for more than 35 days between Oct 05 and Oct 06, you'll have to wait until January 07 to file.
Cheers,