Thanks for following up smacdonald2008. This FP is hot off the press (May 2018) so it'd be good to know where it is. A colleague has also tried to locate it in adobeaemcloud marketplace - just to make sure it's not down to my account credentials.
Is it the case that neither the feature pack 22818 nor the cumulative fix pack for 6.3 - mentioned in my previous comment - are available? Is it normal for the Adobe website to publicise FPs and CFPs that aren't there yet?
How do I get those in the short term? I looked on the licensing site with our customer account but presumably that's not intended to distribute feature packs to customers (?).
I'm the meantime I will (amidst some confusion) raise a support case.