Well, the word I'm hearing is still "around Xmas" which could be before or after - but in other words, no one has said to me "There's been a delay" either.
That said, obviously when they arrive at Turbosat, the UK distributor, they can sell them right away via their website. If smaller sellers have orders in then they'll probably get them on sale a few days after that, allowing for onward shipping. I'd expect that for larger retailers who operate their own distribution systems, it might take a bit longer, if things have to go to a central warehouse and then out again.
Ultimately, when it gets to the UK, it's a matter of logistics after that.
As you can imagine, I'm in pretty frequent contact with the importers about the TF5810 (and the update that will give the TF5800 Freeview Playback). When there's confirmed news, it gets up on the Toppy web site pretty swiftly, so if you use RSS, pick up the news feed from
www.toppy.org.uk/news.php
You can also register your interest on Turbosat's site, too.