I haven't looked in to the fine detail yet, but from what I can see the only change in process is that you need to make a Customs Declaration before the car is presented for VRT inspection, etc. It can be done online and I think there is no impediment to bringing the car here first (as you'd have done before) as long as the entire Customs and VRT transaction is completed within the usual 30 days limit. If the declaration hasn't been made then you won't have the reference number that the VRT folks will now ask for as part of a UK import documentation and procedure.