I don't understand
Nothing has changed in how you pay Road Tax, there's exactly the same online, phone and Post Office options as before. Everyone whose tax expired last night got a reminder in the post around a month ago, as normal. All that's changed (excepting private sales of used cars) is that they don't send you a disc any more, and if you already have one you can take it out of the windscreen today, if you want.
So why has every man and his dog rushed to the website today? Is it vaguely curious types who haven't seen anything in the news about it until today, or people saving up to 20p in bank interest by not taxing their car until it's actually overdue by one day?