You should have kept quiet mate and just used the i.d that came with the shell,you are fooked now as you cannot get rid of the Q plate no matter what and it`ll kill the value of your car and make it harder and more expensive to insure....

If you haven`t already sent off the V5 as scrapped i suggest you just register it in your name and keep the i.d on it that came with the shell otherwise you are pretty fooked...

Sorry for the bad news but keep away from Q plates....