This how I went about getting mine done, might not have the correct way but it worked.
First off get insured, car is not allowed on the road without insurance!
Book MOT, you are allowed to drive to and from MOT station without current MOT as long as you are booked in.
Once MOT'd download application for V5 from DVLA website as well as application for tax disc. fill out as required.
Phone DVLA and ask if you can apply for tax at local office, if the car has been unregistered for over a certain time you can, if not you will have to do it by post and wait for up to three months while they carry out extra checks.
Take all documents, and plenty of cash as well as two forms of ID to DVLA office and wait in a que for an hour, hand over all documents and cash and get your tax disc. Car is now road legal. Then wait until new reg document turns up in the post. Sorted.
daz