He was just scaring you, that would be very heavy handed to issue a Q plate, you would have to be a serial offender (sounds like you are) to get such harsh punishment.
but then if you listen to some conspiracy people, we dont own our vehicles once registered on UK roads (says keeper not owner on V5 for instance) and same with plates, property of DVLA, so they can do what they flippin like eh?!
;-)