A telephone discussion with "ancestry.co.uk" last evening, following a system crash which was apparently global, confirmed that there is no difference between ancestry.com and any other ancestry site - hence the global nature of the failure.
This suggests the duplicate backup hasn't yet been fully set up?
Whilst also discussing the slowness of late, I was again told that it isn't ancestry's fault, but the fault of your browser; their advice is to increase the Firefox cache to 300MB (huh?!) and repeatedly (manually) delete the contents of both IE and Firefox caches.
Blaming some other software or whatever is, of course, as old an excuse as the internet!