So if i was to buy a car now off a private seller as in an emergency purchase I.E. car goes bang, how do i go about taxing it at the post office without a hard copy of the car insurance??? as we all know insurance companies send them out in a few days.... I`m only asking as lately i`ve had to buy a cheap mondeo and then the miggy so i could get to n from work.... so i`m a little confused about how this is going to help the public.... 
So long as the car is mot'd you can tax it online or on helpline,insurance no longer asked for as it can take several days for it to register on the database
Yea, they scrapped the Insurance thing back in December last year, to get things ready for the new system, as Henry says the MID update system was just too slow.
Fairly sure you can Tax at a Post Office now without Insurance proof in place, I taxed one last week on the Automated 0300 Number (having given up trying to do it online) and in effect it checks your MOT Status in seconds, and says something like 'by purchasing the Tax, you are agreeing that you have a valid Insurance in place'.
Seems a backward step to me, allowing people to Tax without proof of insurance, no doubt theres a system in place afterwards if you fall fail of the system.