Seems like TfL have prepared for those trying to renew/sign-up before the the price hike tomorrow, as it is no longer possible to log in to the website. Technical ‘issues’, seems typical of the scheme.
When you go to the page, despite it being the 1st, this is what you get:
Please accept our apologies for the fact that the website is currently unavailable. This is due to planned maintenance, which is scheduled to occur between 00.30 am Thursday 27th of January and 01.15 am Thursday the 27th of December 2012.