I think a fair few have managed to get it to work. I posted back on page 5 or 6 saying mine worked, its just this thread is so long already we can't see all the people that have had no issue.
Personally I ordered at about 08:50 with no issue whatsoever, did a new customer £30 a month with £7.50 unlimited text with a 16Gb Black.
I'd not have had a clue anything was wrong with the site if I hadn't come on here as got no error messages at all, and then got a confirmation email a few seconds later. I've also now had a second email saying the order has been taken to the warehouse. I've also checked it online and it says "in progress" with all the correct options.
The only slight odd thing is now the order tracking doesn't work and just keeps taking saying "thank you for logging in. click here to go back to homepage".
I'm not trying to rub anyone's face in it or anything, just saying that it clearly has worked for some, and we should remember this thread (as with most forums) will be full of those who are having problems (and I do feel for you, I really do) rather than the many (most probably more) who had no issues.